Question

the ten's digit of a number is 5 times the unit's digit . what is the number ?​

Answer 1

The number is 51.

There is only one such number. If you take 2 in the ones place, then the number becomes 102 which doesn't satisfy the above condition that tens placed number should be 5 times the units digit. The same thing happens with numbers greater than 2. So, the only possible units digit which can frame the number according to the condition is 1.

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