The average height of some girls is 138 cm. When 3 boys, with a total height of 372 cm, are included, the average height if the children becomes 132 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
138 |
|
132 |
Total value |
138 u |
372 |
132 u + 396 |
Total height of the girls
= 1 u x 138
= 138 u
Total height of the children = 138 u + 372
138 u + 372 = 132 u + 396
138 u - 132 u = 396 - 372
6 u = 24
1 u = 24 ÷ 6 = 4
Total number of children
= 1 u + 3
= 4 + 3
= 7
Answer(s): 7