Quote:
Originally Posted by shyam.nair
If the number 2484x36y is divisible by 36 find the minimum value of x-y.
ans -7
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36 = 2^2 * 3^2
Hence for 2484x36y to be divisible by 36 it should be divisible by 4 and 9.
Divisibility by 4:
Last 2 digits should be divisible by 4
Hence (6y MOD 4) = 0
Putting y = 0, 1, 2, 3, ..... 9
Only for y = {0, 4, 8} is 6y divisible by 4
Divisibility by 9:
Sum of digits must be divible by 9
Hence (2+4+8+4+x+3+6+y) MOD 9 = 0
or, (27+x+y) MOD 9 = 0
27 is divible by 9
Therefore, (x+y) MOD 9 = 0
x = {9, 5, 1} (As y = {0, 4, 8}
For min value of x-y (x should be min while y should be max)
x = 1
y = 8
x - y = 1 - 8 = -7
Puys hope the approach is correct