I can't tell the numbers apart as there are no colours so I did one answer a with them all being one digit numbers and another answer as them being 2 digit numbers...
1 digit:
5 + 4 + 3 + 3 + 2 + 2 +1 = 20
20 ÷ 7 = 2.86
2 digit:
54 + 33 + 22 + 1 = 110
110 ÷ 5 = 22
A. Multiple the input by 11.
To estimate, round 3102 to 3100
round 1-10 to 2500
1-70 to 2100
1-80 to 2900
2900+2100+2500+3100=10600mi
Yes it is reasonable because you add and subtract numbers when estimating, however it is not exact