The average height of some girls is 128 cm. When 3 boys, with a total height of 321 cm, are included, the average height if the children becomes 119 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
128 |
|
119 |
Total value |
128 u |
321 |
119 u + 357 |
Total height of the girls
= 1 u x 128
= 128 u
Total height of the children = 128 u + 321
128 u + 321 = 119 u + 357
128 u - 119 u = 357 - 321
9 u = 36
1 u = 36 ÷ 9 = 4
Total number of children
= 1 u + 3
= 4 + 3
= 7
Answer(s): 7