QUESTION

CSAT

Hard

Maths

Prelims 2019

Suppose you have a sufficient amount of rupee currency in three denominations Rs. 1, Rs. 10, and Rs. 50. In how many different ways can you pay a bill of 107107?

Select an option to attempt

Explanation

We need to find how many ways we can make Rs. 107 using Rs. 1, Rs. 10, and Rs. 50 coins.

Equation:

x+10y+50z=107x + 10y + 50z = 107 Where: xx is the number of Rs. 1 coins yy is the number of Rs. 10 coins zz is the number of Rs. 50 coins

Case 1:

z=0z = 0 Equation: x+10y=107x + 10y = 107 Possible values of yy: 0 to 10 (11 solutions)

Case 2:

z=1z = 1 Equation: x+10y=57x + 10y = 57 Possible values of yy: 0 to 5 (6 solutions)

Case 3:

z=2z = 2 Equation: x+10y=7x + 10y = 7 Possible values of yy: 0 to 1 (1 solution)

Total Solutions: 11 (from z=0z = 0) + 6 (from z=1z = 1) + 1 (from z=2z = 2) = 18 solutions

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