The average height of some girls is 129 cm. When 3 boys, with a total height of 333 cm, are included, the average height if the children becomes 123 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
129 |
|
123 |
Total value |
129 u |
333 |
123 u + 369 |
Total height of the girls
= 1 u x 129
= 129 u
Total height of the children = 129 u + 333
129 u + 333 = 123 u + 369
129 u - 123 u = 369 - 333
6 u = 36
1 u = 36 ÷ 6 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9