Mathematics
Find the prime factorisation of the following numbers:
(i) 72
(ii) 172
(iii) 450
(iv) 980
(v) 8712
(vi) 13500
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Answer
(i) 72
| 2 | 72 |
|---|---|
| 2 | 36 |
| 2 | 18 |
| 3 | 9 |
| 3 | 3 |
| 1 |
Hence, 72 = 2 × 2 × 2 × 3 × 3.
(ii) 172
| 2 | 172 |
|---|---|
| 2 | 86 |
| 43 | 43 |
| 1 |
Hence, 172 = 2 × 2 × 43.
(iii) 450
| 2 | 450 |
|---|---|
| 3 | 225 |
| 3 | 75 |
| 5 | 25 |
| 5 | 5 |
| 1 |
Hence, 450 = 2 × 3 × 3 × 5 × 5.
(iv) 980
| 2 | 980 |
|---|---|
| 2 | 490 |
| 5 | 245 |
| 7 | 49 |
| 7 | 7 |
| 1 |
Hence, 980 = 2 × 2 × 5 × 7 × 7.
(v) 8712
| 2 | 8712 |
|---|---|
| 2 | 4356 |
| 2 | 2178 |
| 3 | 1089 |
| 3 | 363 |
| 11 | 121 |
| 11 | 11 |
| 1 |
Hence, 8712 = 2 × 2 × 2 × 3 × 3 × 11 × 11.
(vi) 13500
| 2 | 13500 |
|---|---|
| 2 | 6750 |
| 3 | 3375 |
| 3 | 1125 |
| 3 | 375 |
| 5 | 125 |
| 5 | 25 |
| 5 | 5 |
| 1 |
Hence, 13500 = 2 × 2 × 3 × 3 × 3 × 5 × 5 × 5.
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Related Questions
State whether the following statements are true (T) or false (F):
(i) If a number is divisible by 4, it must be divisible by 8.
(ii) If a number is divisible by 3, it must be divisible by 9.
(iii) If a number is divisible by 9, it must be divisible by 3.
(iv) If a number is divisible by 9 and 10 both, it must be divisible by 90.
(v) If a number divides the sum of two numbers, then it must divide the two numbers separately.
(vi) If a number is divisible by 3 and 8 both, it must be divisible by 12.
(vii) If a number is divisible by 6 and 15 both, it must be divisible by 90.
Here are two different factor trees of the number 90. Write the missing numbers:

Write the smallest and the greatest 3-digit numbers and express them as the product of prime.
Write the smallest five digit number and express it in the form of its prime factors.