A9-kg bag of mangoes for $12 dollars per kg

So, each kilogram costs 12 dollars, how much will 9 kilograms cost?

We have to multiply: 9*12=90+18=108 (because 12=10+2, and it's easier to multiply like this:we multuply 10 and 2 separately and then add)

So, a 9-kg bag will cost 108 dollars. !

If you would like to know how much money will you pay for 1-kg bag of mangoes, you can calculate this using the following steps:

9-kg bag of mangoes ... $12
1-kg bag of mangoes ... $x = ?

9 * x = 12 * 1
9 * x = 12      /9
x = 12/9
x = $4/3 = $1 1/3

Result: You will have to pay 1 1/3 dollars per kg.

The first option would be correct if it were one half and not one