SOLUTION: In a group of 14 children some are nine years old and the rest are eleven years old. When the ages of the 14 children are added together the total is 138 years. How many nine-year-

Question 870475: In a group of 14 children some are nine years old and the rest are eleven years old. When the ages of the 14 children are added together the total is 138 years. How many nine-year-old children are there?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
In a group of 14 children some are nine years old and the rest are eleven years old.
let a = no. of 9 yr old kids
let b = no. of 11 yr olds
:
a + b = 14
b = (14-a)
;
When the ages of the 14 children are added together the total is 138 years.
9a + 11b = 138
replace b with (14-a)
9a + 11(14-a) = 138
9a + 154 - 11a = 138
9a - 11a = 138 - 154
-2a = -16
a = -16/-2
a = +8 nine yr old
;
:
Check this, find no. of 11 yr olds: 14-8 = 6
then
8(9) + 6(11) = 138

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