P and Q are two elements which form  P2Q3 and PQ2. If 0.15 mole of P2Q3 weigh 15.9g and 0.15 mole of PQ2 weigh 9.3g , then the sum of the atomic weights of P and Q is _____?

Let atomic weight of P = aand atomic weight of Q = bP2Q30.15 (2a + 3b) = 15.9            2a + 3b = 106    (i)PQ20.15 ( a+2b) = 9.3            a + 2b = 62         (ii)                 (ii) × 2 - (i)2a + 4b = 1242a+3b=106b=18(ii)⇒a + 2 × 18 = 62a = 62 - 36 = 26Therefore,             Atomic weight of P = 26            Atomic weight of Q = 18            26 + 18 = 44