Question 13
MediumOriginal questionHow many positive whole numbers divide 360 exactly (including 1 and 360)?
Show the answer and explanation
CorrectNot quiteAnswer D
Correct answer: D
Explanation
Prime factorisation: .
A divisor takes the power of 2 from 0 to 3 (4 ways), of 3 from 0 to 2 (3 ways), of 5 from 0 to 1 (2 ways).
Divisors .
Worth noting
6 multiplies the exponents , forgetting that each power can also be 0. 9 adds the choices instead of multiplying. 22 leaves out 1 and 360.
- Concept
- Counting divisors with the multiplication rule
- Typical timeTypical
- 70 s
- Your timeYours
- —
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