Answer: 
Step-by-step explanation:
Given
It takes 20 min and 30 min for a person and his friend to paint a wall individually i.e.
In 1 min they cover
part and
part of wall respectively.
If the work together, 1 minute work is

Time required will be reciprocal of it

Answer:
8
Step-by-step explanation:
128-16=112
112÷15(boys+girls)=7.4666666
7.4666666 rounds to 8
When squaring a number, you multiply the number by itself. Ex- 4squared would be 16. 4 x 4 = 16. Ex- 8squared would be 64.
8 x 8 = 64
8000 is 1000 times larger than 8