Mental Math
What do I do? Add or Subtract?
Rounding
Estimating Sums and Differences
Balanced Equations and unknown
100
Use mental math to solve this problem: 24 + 12=?
36
100
Daphne made a poster using 8 red papers and 2 green papers. How many papers did she use in all?
10 papers!
100
Round 78 to the nearest ten.
What is 80
100
Ingrid's class is styding plants. They need 900 plants for the project. They collected 397 plants las week and 204 plants this week. Estimate how many plants they have collected so far.
What is 600 plants.
100
10-n=7 What is the unkown?
n=3
200
How can you find the sum of 33+52 using mental math?
30+50 and 3+2 85
200
Kaeden is reading a book that is 19 pages long. He has read 8 pages of the book. How many pages does he have left to read?
What is 8!
200
Round 832 to the nearest hundred.
What is 800
200
Wesley read 27 pages of a book on Saturday and 31 pages of a book on Sunday. What is the estimate of the total number of pages he read on the two days?
What is 60 pages.
200
Mayte colleted 9 fewer seashells than Alexis. Mayte collected 11 seashells. How many shells did Alexis collect? n-9=11
n=20
300
To subtract 75 - 28 mentally, Bobby subtracted 75-30=45. What should she do next? A. Subtract 45-2 B. Subtract 45-2 C. Add 45+3 D. Add 45+2
B.! 45-2
300
Matthew has 7 stickers and Devon has 6 stickers. Which number sentence shows how many more stickers Matthew has than Devon? A. 7+6=13 B. 7-6=1 C. 7-1=6 D. 13-7=6
B!
300
Round 32 to the nearest ten.
What is 30
300
Ryley asked 359 students if they want to wear pink t-shirts. He asked 228 students. Which number sentence will best help him estimate how many students he has NOT questioned? A. 360-230=130 B. 300-200=100 C. 350-200=150 D. 300-130=270
What is D! you can't round one number the the hundreds and the other to the tens place!
300
It takes Kerel 38 minutes to walk to school. If he has been walking for 26 minutes, how many minutes does Kerel have left to walk? Check if it is reasonable.
38-26=12 40-30=10
400
Use mental math to solve: 32-12=?
What is 20
400
What number sentence is shown? (See picture)
15-7=8
400
Round 389 to the nearest hundred.
What is 400
400
Which 2 numbers have a difference of about 100? A. 110 and 90 B. 215 and 210 C. 335 and 198 D. 532 and 321
What is C!
400
5+4=4+?
5+4=4+5
500
Use mental math to solve: 44+12=?
What is 56
500
A train left the terminal with 87 passengers. At the first top, 52 passengers got off the train, and no passengers got on the train. How many passengers were left on the train?
87-52= 35
500
Round 32 to the nearest hundred.
What is 0
500
Estimate the difference of 315 and 298.
What is 0.
500
Balance the equation. 7+3=5+?
What is 5! 7+3=5+5
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