Mental Math
Safwaan wants to add 473+102 mentally. What should he do first? Choose the correct answer.
A.) Add 2 to 473and add 2 to 102.
B.) Subtract 3 from 473 and add 2 to 102.
C.) Add 2 to 473 and subtract 2 from 102.
D.) Subtract 3 from 473 and subtract 2 from 102.
C.) Add 2 to 473 and subtract 2 from 102.
Round 732 to the nearest 100.
700
Round 77 to the nearest 10.
80
Write the missing numbers that make the equation true.
5+(1+__)=(5+__)+3
3 and 1
Muntaz wants to do mental math to do 526+213. Which is the correct way to break apart the numbers into hundreds, tens and ones.
A.) Break 526 into 500+20+6 and 213 into 200+13.
B.) Break 526 into 500+20+6 and 213 into 200+10+3.
C.) Break 526 into 500+26 and 213 into 200+10+3.
D.) Break 526 into 500+26+6. Break 213 into 200+13+3.
B.) Break 526 into 500+20+6 and 213 into 200+10+3.
Round 449 to the nearest hundred.
400
Round 12 to the nearest 10.
10
Choose all the equations that are true.
1.) 100+170=170+100
2.) 0+93=93
3.) (100+10)+170=110+(10+170)
4.) 32+(4+115)=(32+4)+115
5.) 43+0=0
Equations 1, 2 and 4 are true.
The Village of Hampton has 436 families. 238 of them live within 1 mile of the village square. Use mental math to find how many families live farther than 1 mile from the square. Show your work.
436-238= 198
Round 498 to the nearest hundred.
500
Round 83 to the nearest 10.
80
Yasin subtracts 432 from 668 and gets 236. What addition equation can he use to check his answer?
236+432=
Bisharo wants to subtract 103 from 387 mentally. First she subtracts 3 from 103 to get 100. What should Bisharo's next step be? What is the difference?
A.) Add 3 to 387. The difference is 287.
B.) Add 100 to 387. The difference is 487.
C.) Subtract 3 from 387. The difference is 284.
D.) Subtract 3 from 387. The difference is 287.
C.) Subtract 3 from 387. The difference is 284.
Round 352 to the nearest hundred.
400
Round 69 to the nearest 10.
70
Sundus says that 765-321 is 444. What can she do to check her answer, and is she correct? Choose the correct answer below.
A.) Subtract. 765-300=465. Her original answer was incorrect.
B.) Add. 321+444=765. Her original answer was correct.
C.) Add. 300+444=744. Her original answer was correct.
D.) Subtract. 444-321=123. Her original answer was correct.
B.) Add. 321+444=765. Her original answer was correct.
Use mental math to solve the problem 530-166. Show your work.
530-166= 364
Round 555 to the nearest hundred.
600
Round 95 to the nearest 10.
100
A teenage black bear in a zoo weighs 109 pounds. A mother black bear weighs 168 pounds. Choose all the equations that show a reasonable estimate for how much they weigh together.
1.) 100+200=300
2.) 150+150=300
3.) 110+170=280
4.) 105+165=270
5.) 120+180=300
Equations 1, 3 and 4 are all reasonable estimates.