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Multiplying by 10 and 100
Multiplying by Multiples of 10 and 100
Break Apart Method
Rounding to Estimate
Problem Solving
100
10 x 8
80
100
30 x 9
270
100
26 x 7
26 x 7 = (20 x 7) + (6 x 7) = 182
100
Estimate the product: 34 x 8
240
100
Tanya rounds 15 x 3 to 20 x 3. Will the actual answer be MORE or LESS than the estimate?
Less because 15 rounded up to 20
200
3 x 100
300
200
60 x 7
420
200
341 x 3
341 x 3 = (300 x 3) + (40 x 3) + (1 x 3) = 1,023
200
Estimate the product: 49 x 5
250
200
When Henry estimates 64 x 6 he gets 60 x 6 = 360. Will the actual answer for 64 x 6 be MORE or LESS than the estimate?
MORE because 64 rounded down to 60
300
10 x 6 =
60
300
500 x 8 =
4,000
300
45 x 6
45 x 6 = (40 x 6) + (5 x 6) = 270
300
Estimate the Product: 203 x 6
1,200
300
Vanessa reads every night for 7 nights. On each night, she reads 42 minutes. She estimates that she reads about 350 minutes altogether. Is she correct? If not, about how many minutes does she read?
No, she is not correct. She actually reads about 280 minutes. Vanessa rounded 42 up to 50. It should be rounded down to 40.
400
Lucas reads for 100 minutes per day. He reads for 9 days. How many minutes does he read altogether?
100 x 9 = 900 minutes
400
Alexis is baking 300 holiday cookies for a party. On each cookie, he wants to put 4 M&Ms. How many M&Ms will he need altogether?
300 x 4 = 1,200 M&Ms
400
Jeffrey is busy making beaded keychains for all of his friends. He makes 9 keychains. On each keychain there are 127 beads! How many beads does he use in all?
127 x 9 = (100 x 9) + (20 x 9) + (7 x 9) = 1,143 beads
400
Estimate the product: 617 x 9
5,400
400
Emilio exercises for 28 minutes a day. He does this for 6 days in a row. Emilio estimates that he exercises 180 minutes. Is he correct?
Yes, because 28 rounds to 30. 30 x 6 = 180 minutes.
500
Elisa is growing roses. She has 10 flower pots. In each flower pot there are 7 rose seeds. How many roses will she grow total?
10 x 7 = 70 roses
500
Alina is putting candy canes into bags for Elf Grams. She puts 2 candy canes in each bag. She makes 400 bags in all. How many candy canes does Alina use for all of the Elf Grams?
400 x 2 = 800 candy canes
500
Ava is making an online digital photo album. In each album, she puts 41 pictures. She makes 7 albums total. How many pictures did Ava use altogether?
41 x 7 = ( 40 x 7 ) + ( 1 x 7) = 287 pictures
500
Estimate the product: 459 x 4
2,000
500
Christy multiplies 13 x 6 with the break apart method. In her parentheses she has (10 x 6) and (30 x 6). Her partial products are 60 and 180. Her final answer is 240. Is Christy correct? If not, explain why.
No, Christy is not correct. Her partial products should be 60 and 18. Her final product will be 78.