The average height of some boys is 138 cm. When 3 girls, with a total height of 333 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 |
138 |
|
129 |
Total value |
138 u |
333 |
129 u + 387 |
Total height of the boys
= 1 u x 138
= 138 u
Total height of the children = 138 u + 333
138 u + 333 = 129 u + 387
138 u - 129 u = 387 - 333
9 u = 54
1 u = 54 ÷ 9 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9