Mixed-Rounding (Tens and Hundreds)
Round this number to the nearest ten: 47
50
What is the leading digit for the number 427
4
34+53
87
62-21
41
Leading Digit
(accurate examples count as an acceptable answer)
Round this number to the nearest hundred: 65
100
What is the leading digit for the number 397
3
206+103
409
88-23
65
88-20-3=68-3=65
What does the word Sum mean? What does the word Difference mean?
a) The answer to addition
b) The answer to subtraction
Round this number to the nearest ten: 1,423
1,420
Using Front-End Estimation, find the estimated sum of 452+142
500
400+100=500
86+96
182
34-7
27
34-10+3=24+3
"To check that your answer is reasonable"
Comparing your exact answer to the estimated answer in order to check that your answer makes sense.
Round this number to the nearest hundred: 52,345
52,300
Using Front-End Estimation to subtract 358 from 672
300
94+97
191
200-6-3=200-9
or 94+100-3=194-3=191
72-44
28
72-50+6
What do we call the two strategies when we do mental subtraction with 2-digit numbers?
1. Subtract the tens then the ones
2. Subtract (more) tens then add the extra ones
Tip: Only change the second number and keep the first number the same.
Round the sum to the nearest hundred: 542+137
Is the rounded sum reasonable compared to the exact sum?
a) 700
b) 700 is reasonable compared to 679
Use Front-End Estimation to add 746 and 329
What is the difference between the exact answer and the estimated answer?
b) 75
394+98
492
394+100-2=494-2
0r 400+100-6-2=500-8
445-99
346
445-100+1=345+1
Name four different strategies we have learned to do mental addition
(Hint: two strategies have to do with adding 100 and the other two don't)
1. add the tens then add the ones
2. add (more) tens then subtract the extra ones
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1. add (one) 100 then subtract the extra ones
2. add the hundreds then subtract the extra ones
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Tip: Only change the second number and keep the first number the same.