1.

x gram of water at 40 degrees celsius is mixed with 4 grams of water at 90 degrees celsius the final temperature of the water is 50

Answer» <html><body><p>since it is given that <a href="https://interviewquestions.tuteehub.com/tag/50-322056" style="font-weight:bold;" target="_blank" title="Click to know more about 50">50</a> gm water at 20 ⁰ C and 50 gm of water at 40⁰ C are mixed.  Since the masses of the <a href="https://interviewquestions.tuteehub.com/tag/liquid-1075124" style="font-weight:bold;" target="_blank" title="Click to know more about LIQUID">LIQUID</a> at different temperatures are same, the answer is very easy and simple :  average of 20⁰C and 40⁰C.  that is:  30⁰C.Explanation: final temperature of the <a href="https://interviewquestions.tuteehub.com/tag/mixture-1098735" style="font-weight:bold;" target="_blank" title="Click to know more about MIXTURE">MIXTURE</a> =       = [ m1 * T1 + m2 * T2 ] / (m1 + m2)     = [ 50 gm * 20⁰ C + 50 gm * 40⁰C ]  / (50+50)       = 3,000 / 100 = 30⁰C  another way using specific heats :     let the final temperature be = T ⁰C   Amount of heat given out by the hot water = m * s * (40⁰C - T)           = 50 gm * s* (40 -T)   Amount of heat taken in by the <a href="https://interviewquestions.tuteehub.com/tag/cold-921390" style="font-weight:bold;" target="_blank" title="Click to know more about COLD">COLD</a> water = m * s * (T - 20⁰C)       = 50 gm * s * (T - 20 )     As the amounts are equal, because the heat is transferred from hot water to the cold water without any loss of heat to any surroundings,           50 * s * (40 -T) = 50 gm * s  * (T-20)                   40 - T = T - 20             2 T = 60    =&gt; T = 30⁰C</p></body></html>


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