The average height of some boys is 147 cm. When 3 girls, with a total height of 405 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 |
405 |
144 u + 432 |
Total height of the boys
= 1 u x 147
= 147 u
Total height of the children = 147 u + 405
147 u + 405 = 144 u + 432
147 u - 144 u = 432 - 405
3 u = 27
1 u = 27 ÷ 3 = 9
Total number of children
= 1 u + 3
= 9 + 3
= 12
Answer(s): 12