The average height of some girls is 144 cm. When 3 boys, with a total height of 396 cm, are included, the average height if the children becomes 138 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
144 |
|
138 |
Total value |
144 u |
396 |
138 u + 414 |
Total height of the girls
= 1 u x 144
= 144 u
Total height of the children = 144 u + 396
144 u + 396 = 138 u + 414
144 u - 138 u = 414 - 396
6 u = 18
1 u = 18 ÷ 6 = 3
Total number of children
= 1 u + 3
= 3 + 3
= 6
Answer(s): 6