The average height of a group of boys was 164 cm. After 5 girls with a total of 860 cm joined the group, the average height of all the students increased to 166 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Students |
Number |
1 u |
5 |
1 u + 5 |
Value |
164 |
? |
166 |
Total value |
164 u |
860 |
166 u + 830 |
(a)
Average height of girls
= 860 ÷ 5
= 172 cm
(b)
Total height of students
= 166(1 u + 5)
= 166 u + 830
Total height of boys and girls = 164 u + 860
166 u + 830 = 164 u + 860
166 u - 164 u = 860 - 830
2 u = 30
1 u = 30 ÷ 2 = 15
Number of boys = 15
Answer(s): (a) 172 cm; (b) 15