The average height of some girls is 130 cm. When 3 boys, with a total height of 342 cm, are included, the average height if the children becomes 126 cm. How many children are there altogether?
|
Girls |
Boys |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
130 |
|
126 |
Total value |
130 u |
342 |
126 u + 378 |
Total height of the girls
= 1 u x 130
= 130 u
Total height of the children = 130 u + 342
130 u + 342 = 126 u + 378
130 u - 126 u = 378 - 342
4 u = 36
1 u = 36 ÷ 4 = 9
Total number of children
= 1 u + 3
= 9 + 3
= 12
Answer(s): 12