Please first see the full image and then give answer
Answers
So we need to first round each number to their nearest tens to get an estimated answer.
When we round numbers to nearest tens, we use following steps.
- We round the number up to nearest 10 if the last digit in the number is 5, 6, 7, 8, 9. Example: After rounding 25, 26, 27, 28, 29 to nearest ten we will get 30.
- We round the number down to nearest 10 if the last digit in the number is 1, 2, 3, 4. Example: After rounding 21, 22, 23, 24 will get 20.
When we look at the number line we can see that these are closer to 20 whereas the numbers after 24 are closer to 30.
- If the last digit is already 0 then rounding is not required as it is already to the ten.
There is an error in the example given to us. Rounded form of 81 is 80 and 68 is 70. After subtracting 70 from 80, the answer comes out to be 10. But in the example they have added the values.
_________________
1. We will be using above steps in all the parts of the question.
98 ==> 100 and 29 ==> 30
Subtracting now,
100-30 = 70
Hence, the estimated answer is 70
_________________
2.
24 ==> 20 and 44 ==> 40
Adding,
20+40= 60
Hence, estimated value is 60.
_________________
3.
73 ==> 70 and 17 ==> 20
Adding
70+20= 90
Ans: 90
________________
4.
53 ==> 50 & 33 ==>30
Adding
50+30= 80
Ans: 80
________________
5.
97 ==> 100
78 ==> 80
Subtracting
100 -80 =20
Ans: 20
________________
6.
81 ==> 80 & 55 ==> 60
Adding
80+60 = 140
Ans: 140
_________________
7.
32 ==> 30 & 18 ==> 20
Subtracting
30 -20 = 10
Ans: 10
_________________
8.
46 ==> 50 & 64 ==> 60
Adding
50 + 60 = 110
Ans: 110
__________________
9.
34 ==> 30 and 68 ==> 70
Adding
30 + 70 = 100
Ans: 100
___________________
10.
97 ==> 100 and 94 ==> 90
Subtracting
100 - 90 = 10
Ans: 10
___________________
11.
75 ==> 80 and 21 ==> 20
Subtracting
80 - 20 = 60
Ans: 60
Hope it helps you.