Final answer:
Using the rule provided, Sian's 20 miles cycling is equivalent to 32 kilometers, as shown by the conversion process. The options give different mile values, not the kilometers Sian has traveled. None of the provided choices match the correct converted distance.
Step-by-step explanation:
The student has cycled 20 miles and needs to convert miles to kilometers. According to the provided rule, to convert miles to kilometers, one would use the relationship of miles to kilometers as shown: Number of miles = 5 × Number of kilometers / 8. We need to invert this relationship to find how many kilometers are equivalent to the miles cycled by Sian.
To do this we solve for kilometers if miles are known:
- Let number of kilometers = K
- 20 miles = 5 × K / 8
- Multiplying both sides by 8 to isolate K on one side: 160 = 5 × K
- Dividing both sides by 5: K = 160 / 5 = 32 kilometers
Therefore, Sian cycled 32 kilometers.
To double-check if it's a reasonable answer, we can look at the approximate conversion factor of 1 mile being roughly equal to 1.61 kilometers:
- 20 miles × 1.61 km/mile ≈ 32.2 km
This confirms that our conversion was performed correctly. So the answer is none of the options (a) 50 miles, (b) 40 miles, (c) 32.5 miles, or (d) 25 miles.