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Playing with numbers

  • Any two-digit number ab, made of digits a and b, can be written in general form as ab = 10a + b whereas the number ba can be written as ba = 10b + a.

For example, 45 = 4 × 10 + 5 and 54 = 5 × 10 + 4

  • A three-digit number abc, made of digits, a, b, and c, can be written in general form as abc = 100a + 10b + c.

For example, 456 = 4 × 100 + 5 × 10 + 6

  • The sum of a two-digit number and the number formed by reversing the digits is always a multiple of 11.

For example, 28 + 82 = 110 = 11 × 10 is a multiple of 11.

  • The difference between a two-d…

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