The average height of some boys is 136 cm. When 3 girls, with a total height of 303 cm, are included, the average height if the children becomes 129 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
136 |
|
129 |
Total value |
136 u |
303 |
129 u + 387 |
Total height of the boys
= 1 u x 136
= 136 u
Total height of the children = 136 u + 303
136 u + 303 = 129 u + 387
136 u - 129 u = 387 - 303
7 u = 84
1 u = 84 ÷ 7 = 12
Total number of children
= 1 u + 3
= 12 + 3
= 15
Answer(s): 15