Question

given that the energy E,varies directly as the resistance R,as the square of the distance D, obtain an equation connecting E,R and D.E=32/25 when R=8 and D=5 calculate the value of R when E=16 and D=5

Answer 1

E = kRD^2
So,
(32/25)=(8*5^2)k
E = 4/625 RD^2
Now use your values to find the desired R.

Answer 2

E =kRD^2. So(32/25)=(8*√5)K crossmultiply =32 /25=8k/25. 800=200k. Divide both sides by 200. 800/200=200/200k. K=4. Calculate value of R when E=16,d=3,k=4. 16×4×R/√3.cross multiply. 4r=16×9. 4r=144. Divide both sides by 4. 4r/4=144/4. R=35