Advertisements
Advertisements
प्रश्न
Sunscreens block harmful ultraviolet (UV) rays produced by the sun. Each sunscreen has a Sun Protection Factor (SPF) that tells you how many minutes you can stay in the sun before you receive one minute of burning UV rays. For example, if you apply sunscreen with SPF 15, you get 1 minute of UV rays for every 15 minutes you stay in the sun.
Suppose a sunscreen allows 25% of the sun’s UV rays.
- What fraction of UV rays does this sunscreen block? Give your answer in lowest terms.
- Use your answer from Part (a) to calculate this sunscreen’s SPF. Explain how you found your answer.
Advertisements
उत्तर
a. Sunscreen allows 25% of the sun’s UV rays.
∴ It blocks UV rays = 100 – 25 = 75%
= `75/100`
= `3/4`
b. Sunscreen allows 25% on `3/4` of UV rays.
It means, it protect = `1 - 3/4 = 1/4` of UV rays.
Hence, it’s a SPF 4.
APPEARS IN
संबंधित प्रश्न
A man got a 10% increase in his salary. If his new salary is Rs 1,54,000, find his original salary.
Mohan's income is Rs 15500 per month. He saves 11% of his income. If his income increases by 10%, then he reduces his saving by 1%, how much does he save now?
The number of illiterate persons in a country decreased from 150 lakhs to 100 lakhs in 10 years. What is the percentage of decrease?
In the year 2015 ticket to the world cup cricket match was ₹ 1,500. This year the price has been increased by 18%. What is the price of a ticket this year?
15% increase in price of an article, which is Rs 1,620, is the increase of Rs ______.
Four times a number is a ______ % increase in the number.
Three times a number is 200% increase in the number, then one-third of the same number is 200% decrease in the number.
Number of students appearing for class X CBSE examination increases from 91,422 in 1999 – 2000 to 11,6054 in 2008 – 09. Increase in the number of students appeared is approximately 27%.
If A is increased by 20%, it equals B. If B is decreased by 50%, it equals C. Then ______ % of A is equal to C.
