BMAT 2010 Q 12 Math question

[Aung_Htet_Thar]

Got no idea how to solve it:))

[Juliette]

hi

total time group 1:
x/20=54 so x = 20 * 54 = 1080
total time group 2:
x/P = T so x = PT

new mean:
(1080+PT)/(20+P) = 56
1080+PT = 1120 + 56P
PT - 56P = 40
P(T - 56) = 40
P = 40/(T-56) option C)