Which of the following, when mixed, would raise the temperature of 20 g of water at 30oC most?

Let m grams of water whose temperature is θ0 (> 30oc) and specific heat is 1 cal/g-oC be added to 20 g of water at 30oC and let )be the final temperature of mixture. m(1)θ0−θ=(20)(1)(θ−30)∴ θ=600+mθ020+mThe right-hand side is maximum for option (d). Therefore, the correct answer is (d).