Physics (A man in the lift)
posted by Ahsanur .
A man of mass m is standing in an elevator. The elevator is accelerating downward at g/k, where k>1 and g is the gravitation acceleration. If the force on the man by the elevator's floof jmg, where j is a constant and k= a/(b+cj), where gcd(a,b,c)=1, what is a+b+c? If k cannot be expressed in this form, say so.

mg down
F up
mg  F = m a = m g/k
mg  jmg = (mg/a)(b+cj)
1j = (b+cj)/a = 1/k
k (1j) = 1
I do not know what gcd(a,b,c)=1 means so can go no further.