The average height of some boys is 143 cm. When 3 girls, with a total height of 384 cm, are included, the average height if the children becomes 138 cm. How many children are there altogether?
|
Boys |
Girls |
Total |
Number |
1 u |
3 |
1 u + 3 |
Value |
143 |
|
138 |
Total value |
143 u |
384 |
138 u + 414 |
Total height of the boys
= 1 u x 143
= 143 u
Total height of the children = 143 u + 384
143 u + 384 = 138 u + 414
143 u - 138 u = 414 - 384
5 u = 30
1 u = 30 ÷ 5 = 6
Total number of children
= 1 u + 3
= 6 + 3
= 9
Answer(s): 9