The average height of some boys is 147 cm. When 3 girls, with a total height of 411 cm, are included, the average height if the children becomes 144 cm. How many children are there altogether?
| |
Boys |
Girls |
Total |
| Number |
1 u |
3 |
1 u + 3 |
| Value |
147 |
|
144 |
| Total value |
147 u |
411 |
144 u + 432 |
Total height of the boys
= 1 u x 147
= 147 u
Total height of the children = 147 u + 411
147 u + 411 = 144 u + 432
147 u - 144 u = 432 - 411
3 u = 21
1 u = 21 ÷ 3 = 7
Total number of children
= 1 u + 3
= 7 + 3
= 10
Answer(s): 10
