Answer: C) 16 $ Explanation: Let the 1 day work of a boy=b and a girl=g, then2b + g = 1/5 ---(i) andb + 2g = 1/6 ---(ii)On solving (i) & (ii), b=7/90, g=2/45As payment of work will be in proportion to capacity of work and a boy is paid $ 28/week, so a girl will be paid 28×245790 = 16 $.

Answer: A) QQJGZXRIKSGRM Explanation: The first three letters are coded as same positioned letters from the right end of the alphabet. So are the seventh to tenth letters. The fourth , fifth and sixth letters move one, two and three positions forward respectively in the alphabet. So, do the last three letters. Thus, CONCENTRATION => XLMDGQGIZGJQQ Now reverse this and we get QQJGZIGQGDMLX

Clearly, marked price of the book = 120% of C.P
Also, cost of paper = 25% of C.P.
Let the cost of paper for a single book be Rs. n.
Then, 120 : 25 = 180 : n ⇒ n = Rs.  = Rs. 37.50