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Rekha says: 'Every number divisible by 3 is also divisible by 9.' Which number proves her wrong?

Class 6Playing with NumbersPlaying with Numbers
  • A18
  • B27
  • C36
  • D12

Step-by-Step Solution

1 + 2 = 3, so 3 divides 12 , but 12 ÷ 9 leaves remainder 3. The rule only runs the other way: since , every multiple of 9 is a multiple of 3. The traps 18, 27 and 36 are all multiples of 9, so none of them can disprove anything.
Answer: D) 12

Key idea: Factors come in pairs

To find every factor of a number, walk up from 1 and check each whole number — if it divides the number with no remainder, it is a factor. Factors come in **pairs**: if 4 is a factor of 12, so is 12 ÷ 4 = 3. So you only need to check up to the square root of the number to find them all. Factors of 12: — six factors total: 1, 2, 3, 4, 6, 12. Every number has 1 and itself as factors.

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