Kelly subtracted 2.3 from 20 and git 17.7 explain why this answer is reasonable
What is it
Suppose an expresso coffee costs you $2.30 , you hand over a $20 bill.
What is the change you should get back?
20 - 2.3 = .....
To explain why the answer, 17.7, is reasonable, let's follow the steps Kelly took when subtracting 2.3 from 20.
First, let's start with 20. When subtracting, we are essentially taking away a certain amount from the original number. In this case, 2.3 is being subtracted from 20.
To perform the subtraction, we line up the decimal point in both numbers and subtract each column from right to left. Starting from the rightmost column, we have:
20.0
-2.3
------
1.7
Subtracting 3 from 0 in the rightmost decimal column is not possible, so we borrow from the tens place (represented by the 2 in 20.0) and increase the value of the 0 to 10. Now, we have:
20.0
-2.3
------
10.7
Now, subtracting 3 from 10 in the rightmost decimal column gives us 7.
So, the result of subtracting 2.3 from 20 using the above steps is 17.7.
This answer is reasonable because subtracting 2.3 from 20 results in a smaller number since 2.3 is being taken away. Additionally, the resulting number, 17.7, falls between 0 and 20, confirming that the subtraction was done correctly.
Thus, we can conclude that the answer, 17.7, is reasonable based on the subtraction process and the relationship between the two original numbers.