Four boys and ten girls can cut a field first i... - JAMB Mathematics 2020 Question

Let x = numbers of boys that can work at \(\frac{5}{4}\) the rate as 10 girls 

Then,

1 hrs, x boys will work for \(\frac{\frac{1}{5} \times 10}{4}\) 

x = \(\frac{5}{4}\) x 10 

= 8 boys 

This means that 8 boys will do the work of ten girls at the same rate 

4 + 8 = 12 boys cut the field in 5 hrs for 3 hrs, 

\(\frac{12 \times 5}{3}\) boys will be needed

= 20 boys.