The average height of some girls is 135 cm. When 3 boys, with a total height of 345 cm, are included, the average height if the children becomes 130 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
135 |
|
130 |
Total value |
135 u |
345 |
130 u + 390 |
Total height of the girls
= 1 u x 135
= 135 u
Total height of the children = 135 u + 345
135 u + 345 = 130 u + 390
135 u - 130 u = 390 - 345
5 u = 45
1 u = 45 ÷ 5 = 9
Total number of children
= 1 u + 3
= 9 + 3
= 12
Answer(s): 12