Lesson 115 Date Estimating answers to word problems by rounding to the nearest hundred or thousand Estimating can be used to quickly check numbers to see if they make sense. For example, if you need to multiply 38 by 6, you can estimate by multiplying 40 by 6. If you know 4 times 6, you can do this in your head and get 24. Add a zero to get an estimate of 240. Your answer to 38 times 6 should be close to 40 times 6. Guided Practice Tom walked south on River Rd. After crossing Beach Ave., he saw a friend on the east side of River Rd. His friend was on the side of the street. How many sixths are in 3 wholes? A 48 Can you explain why three-digit numbers are often rounded to the nearest hundred and four-digit numbers are rounded to the nearest thousand? 3. left 4. right 3 x (3 x 3) = The closer the original number is to the rounded number, the closer the estimate will be to the exact answer. Can you explain why? For each number that is to be rounded, underline the determining digit. Marian has 2 extra tickets to the opera so she can invite 2 friends to come with her. Mary Lou, Phyllis, Jan and Darlene would like to go. How many possibilities does she have for sharing the extra tickets? Select the correct process. 2 3 = 6 + - x 26. 27. 28. 29. B 43 1 2 Ed drove 152 miles on Monday, 238 on Tuesday and 176 on Wednesday. Estimate the total miles he drove. Notice that the estimate is not the exact answer. In one year, Chris bought a car, a washer and dryer, and a computer with printer. He bought the car for $6,152, the washer and dryer together for $1,512, and the computer for $1,150. Estimate the total spent on these three items. www.excelmath.com 3273 Celsius 25 20 15 10 5 Average Temperature Fall Winter Spring Summer How much warmer is it in the spring than in the winter? How much cooler is it in the fall than in the summer? 4 0 5 = How much would the average fall temperature need to increase to be the same as the spring? C 30
Guided Practice 115 Leslie has four nickels, nine dimes and three quarters. How much money does she have? Three stamps cost 15. How much does one stamp cost? D $1.90 It is 6 A.M. 7 hours It is 10 P.M. In 5 hours it E 94 ago it was. will be. ( 6 7, 6 1, 5 5, 4 9,, ) Measure each line segment to the nearest half centimeter. F 28 1 2 Fill in the chart. Select the correct symbol G 47 I J IJ = cm Tricycles 1 2 3 4 5 6 7 3 + 9 3 x 4 K KL = cm L Tires 3 6 9 15 18 21 < = > 26. 27. 28. M MN = cm For a school picnic, Lucas bought 21 pounds of grapes, 28 pounds of apples, 15 pounds of strawberries, 18 pounds of hot dogs and 22 six packs of sodas. Estimate how many pounds of fruit he bought. 5 tons 6 meters 7 pounds 8 grams N A cat might weigh. 40. cone 50. sphere 60. cube H 137 Bob bought several pens. He received I 13 $13.10 in change. What information do you need so you will know how much money he gave the clerk? 7 x B = 2 8 B = 3. the cost of each pen 4. the number of quarters he gave the clerk 5. the cost for all the pens 1 2 are shaded. B = 1 C = 4 C B = www.excelmath.com 3274
Test 20 # Date 1 2 3 4 5 5 2 3 2 0 1,8 9 6 + 2 5 1 $ 3.0 1-2.0 6 4 3 1-2 3 2 8 1 x 4 7 8 9 Select the correct symbol. > < = 4 + 3 9-3 4 9 something that has the same shape as a cylinder. 11 12 13 Two pies are cut into fourths. How many pieces will there be? 9 0 7 x 3 1 5 6 6 6 10 3 < 9-7 3 5 Put a T if the statement is true or an NT if the statement is not true. 9 0 14 15 8 - ( 6 + 1 ) = 5 - A pentagon has sides. 16 A card costs $ 1.91. Tom bought four cards and gave the clerk a five-dollar bill and three one-dollar bills. How much was his change? 17 18 Carol paid $25 for a skirt. A blouse she bought was $9 less than the skirt and a coat she got was $30 more than the blouse. How much did her coat cost? The spinner will most likely stop on a. 19 Rob went to the store to buy bread. Which of these events happened third? He put the bread into the basket on his bicycle. 20 A second grade teacher bought 20 pencils, 15 pens and 10 notebooks for five children. She divided everything equally among them. Each child got He asked for directions to the bread section. pencils, pens and notebooks. He got his change. He selected the bread he wanted. www.excelmath.com 3275
Create A Problem 20 More than one way to solve a problem Katie and Sarah are twins. They look alike but do things differently. They always debate the best way to solve a math problem. For example, A card costs $ 1.93. Fred bought four cards at the store. He gave the clerk a five-dollar bill and three one-dollar bills. How much was his change? Katie says: Sarah says: I do this problem in 3 steps. 1. I calculate the total amount Fred gave the clerk $5 + $1 + $1 + $1 = $8 2. I find out how much the 4 cards cost $1.93 x 4 = $7.72 3. I subtract the cost from the total to get his change $8.00 - $7.72 = $.28 I do this problem in my head. I find that Fred gave the clerk $8 I estimate a card is $2, so there won't be much change. I subtract $1.93 from $2.00 and get 7 cents. Fred gave the clerk 7 cents too much for each card. I multiply 7 times 4 to get $.28 change! Katie used to weigh 102 pounds. She gained 8 pounds, but then lost 5 pounds. How much does she weigh now? [Tell how Katie and Sarah could have solved this math problem in two different ways.] www.excelmath.com 3276
Lesson 120 Date Recognizing figures that are similar or congruent; recognizing flips (reflections), slides (translations), and turns (rotations) When two figures are similar, they have the same proportions, but not the same size. Each pair shows two similiar figures. A slide (translation) occurs when a figure moves without changing its appearance. Each of these shows a slide. 10 11 12 1 2 3 A turn (rotation) occurs when a figure turns around a point. Each of these shows a turn. When two figures are congruent, their angles and lengths of sides are identical. Each pair shows two congruent figures. 4 5 6 13 14 15 T T When a figure is moved to another position, the change is called a transformation. Three transformations are flip (reflection), slide (translation) and turn (rotation). Indicate how each figure has moved by writing flip, slide or turn. 16 17 18 A flip (reflection) occurs when a figure moves across a straight line in such a way that the new position is a mirror image of the first position. Each of these shows a flip. The new position is the same distance from the straight line as the original position. 7 8 9 19 20 21 M M www.excelmath.com 3285
Guided Practice 120 2 ft 1 ft Which of these numbers is closest to 55? 6 3 4 5 3 7 A 76 Andrea can buy nails in B 29 packages of four. Which 8 x M = 3 2 A = 4 B = 5 set shows the number of nails she might buy? M = A + B = perimeter = 6. (12, 18, 24, 30) 7. (8, 16, 24, 30) (8-5) + 4 = 8. (8, 12, 24, 28) 9. (6, 10, 14, 18) 4 quarts = pints Measure each line segment to the nearest half inch. A AB = in B C 11 1 2 Select the number from the given set to fill in the blank. (3,241 ; 2,431 ; 4,312 ; 3,421) one thousand, four hundred D 6,901 E EF = in F 3,240 > 3 thousands and 7 tens C D CD = in Over the last three months Megan earned $3,258, $2,395 and $2,703. The best estimate for how much she earned is between. 6. $5,500 and $6,500 7. $6,500 and $7,500 8. $7,500 and $8,500 9. $8,500 and $9,500 Apples are sold 7 to a bag. How many apples will there be in 14 bags? E 106 The distance from Dallas to E F 31 Chicago would be measured B in. A D EC is 16. liters 18. kilograms 5. a radius. 17. miles 19. yards C 6. a diameter. 7. the circumference. 3 + (9-5) = + (4-0) 8 - (7-1) = (3 + 4) - www.excelmath.com 3286
Test 21 # Date 1 2 3 4 5 6 3 6 2,5 0 2 1 9 6 + 1,2 7 7 3 6 9 3 7 2 0 1-9 3 4 5-1 3 8 2 9 4 0 3-1 2 3 (8 3, 7 7, 7 1, 6 5,, ) 3 0 4 x 7 7 8 9 10 11 4 2 x 6 12 13 14 What are the missing numbers? 4 feet = inches 9 6 2 x 3 How many fifths are there in 3 wholes? 4 + (8-3) = (3 + 4) + 15 16 It is 4 A.M. 7 hours ago it was. Every day Monica swims two miles, rides her bike 12 miles and then runs half the distance that she rides her bike. How far does she go in a week? 17 18 3 gallons = quarts Pat had $9. He bought a game that cost $3.77. He paid for it with a five dollar bill. Does he have enough money left to buy a video for $5.25? 19 20 Patrick is younger than Alan but older than Ruth. Keith is younger than Alan. Who is the oldest? Six years ago there were four stop lights in Jerry's town. Today there are three times as many stop lights as there were two years ago. How many stop lights are there in his town now? What information is needed to answer the question? www.excelmath.com 3287
Create A Problem 21 Bring Your Pet to Work Day? Write a story problem about time and one about money. Solve your two problems. Manny and Natalia worked at a small company. Neither of them had children, so they couldn't bring anyone on "Bring Your Child to Work Day." They asked if they could bring their pets to work. The boss said, "Yes, as long as you don't bring cats and dogs on the same day." Manny brought his cat Tiger on Friday at 7:00 A.M. What a surprise! Tiger cried, howled, whined and gurgled. Manny didn't realize how much noise Tiger would make. Natalia said he was just scared and gave Tiger some love. At least 10 of the people in the office came by to see the cat. By 9:00 Tiger was calm. He climbed on the computer and looked down at Manny. He jumped onto a keyboard, knocked over a $2.50 cup of coffee and ruined a 3-page report. Then he fell asleep on Natalia's new red sweater. Everyone was laughing except Manny and Natalia. At lunchtime the boss said Manny had been there for 5 hours but had only worked about 10 minutes. He would still pay Manny $12 an hour for Friday, but said "NO MORE PETS AT WORK!" www.excelmath.com 3288