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Multiplying by 10's and 100's
Using Mental Math
Rounding
Reasonableness
Expanded Algorithm
100
7x10=
What is 700
100
3x18=
What is 54
100
Round 125 to the nearest ten.
What is 130
100
Is it reasonable to say that 32x8=160?
What is no, 8x30=240
100
Use Expanded Algorithm to solve 16x2
What is 32
200
9x20=
What is 180
200
33x4=
What is 132
200
Estimate 39x5=
What is 200
200
Is it reasonable to estimate 62x5=300?
What is yes, 60x5=300.
200
Use expanded algorithm to solve 27x3
What is 81
300
5x60=
What is 300
300
42x8=
What is 336
300
Estimate 7x314=
What is 2,100
300
Is it reasonable to say that 487x3=150?
What is no, 500x3=1500
300
Use expanded algorithm to solve 23x5
What is 115
400
6x600=
What is 3,600
400
The height of one scuba diver is about 6 feet. The longest blue whale on record was about 18 scuba divers in length. Use break apart to estimate the length of the blue whale.
What is 108 feet.
400
Estimate 249x4=
What is 1,000
400
A student solved the problem m-16=54 and got m=38. Is the answer reasonable? Why or why not?
What is m=38 is not reasonable, it has to be larger than 54.
400
Use expanded algorithm to solve 9x76
What is 684
500
800x9=
What is 7,200
500
A student used the break apart method to multiply 42x8 and got 324 for an answer. What did they do wrong?
What is she forgot to multiply 8x2 (teacher check).
500
An adult female bald eagle has a wingspan that is about 7 feet long. If there are 12 inches in a foot, how long would you estimate a female Bald Eagle's wingspan is in inches?
What is about 70 inches.
500
Write a problem about fish that would have an answer NEAR 80. Then solve AND use an estimate to show your answer is reasonable.
What is teacher checks.
500
Use expanded algorithm to solve: If all 16 students in Mrs. VanEps 4th grade class bring in 8 pieces of candy for Halloween, how much candy will the entire class have?
What is 128 pieces of candy.