A rainy day occurs once in every 5 days. One-quarter of the rainy days produce rainbows. The percentage of days having no rainbows is:

Correct option is C

Given:
Frequency of rainy days = 1 in 5 days
Probability of rainbows on rainy days = 1/4
Solution:
The question essentially asks for the percentage of total days that are rainy but produce no rainbows.
Percentage of rainy days out of total days:
Rainy days = $$\frac{1}{5} = 20\%$$​​
If one-quarter of rainy days have rainbows, then three-quarters of rainy days have no rainbows.
Percentage of rainy days having no rainbows:
​$$\frac{3}{4} × 20\% = 15\%$$​​
Final Answer
So the correct answer is (c)