The quantity of heat needed to melt ice = mL (where m is the mass of ice and L is the specific latent heat of fusion of ice)
Q = 50×336=16800 J50 \times 336 = 16800\,\mathrm{J}50×336=16800J but this is 70% of the total heat supplied so that we have,
70% total heat = 16800J
70100\; \frac{70}{100}10070 of total heat = 16800J
⇒ Total heat supplied = 16800×10070=24000 J\; \frac{16800 \times 100}{70} = 24000\,\mathrm{J}7016800×100=24000J
