exam Maths Puzzle Numerical Ability

I need help please...I dont understand....it reads as follows:
L varies inversely as W. Find the constant of variation if L=40 and w=50

Read Solution (Total 0)

exam Other Question

Find the sum of each geometric series described
1. asub1= 512 r=1/2 n=6
2. 3 + 6 + 12...+192
3. asub1= -2 asub5= -162 n=7 (3^3)^2/ (3)

THIS IS HOW I WORKED THIS PROBLEM. IS IT CORRECT? Thanks

=(3^6) / (3)
= 1^6