The average height of some girls is 138 cm. When 3 boys, with a total height of 351 cm, are included, the average height if the children becomes 131 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
138 |
|
131 |
Total value |
138 u |
351 |
131 u + 393 |
Total height of the girls
= 1 u x 138
= 138 u
Total height of the children = 138 u + 351
138 u + 351 = 131 u + 393
138 u - 131 u = 393 - 351
7 u = 42
1 u = 42 ÷ 7 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9