CAT Exam Model Paper 5 with solutions for free online practice

All numbers are of the form 4K or 4K+1 or4K + 2or 4K + 3.
The coins are available in the denominations of 4,8, 13 and 18.
Since we have infinite 4’s
(a) We can make every number of the form 4K.
(b) We can make every number of the form 4K + 1 starting with 13.
(c) We can make every number of the form 4K + 2 starting with 18.
(d) We can make every number of the form 4K + 3 starting with (18 + 13) i.e. 31.
So among these the largest number that is not possible is a number of the form 4K + 3 less than 31, which is 27. So the sum of the digits is 9.