Question

We are given the following numbers: 13, 14, 22, 52, 63, 74. Calculate a by adding the numbers and then rounding the sum to the nearest ten. Calculate b by first rounding each number to the nearest ten and then adding the rounded numbers. What is a-b?

Answer 1

a-b=10

Explanation:

add all the numbers then round

13+ 14+ 22+ 52+ 63+ 77=241

Round to the nearest ten

a =240

first rounding each number to the nearest ten and then add

13+ 14+ 22+ 52+ 63+ 77

10+10+20+50+60+80 =230

b= 230

a-b = 240-230

= 10

Answer 2

20

Explanation:

First let's calculate a. The sum of the numbers is 13+14+22+52+63+74=238. 238 rounded to the nearest ten gives us a=240.

Now let's calculate b. Rounding 13, 14, 22, 52, 63, 74 each to the nearest ten, we get 10, 10, 20, 50, 60, 70 respectively. This means that b=10+10+20+50+60+70=220. Therefore, a-b=20

help from AoPS