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.
1. A sunscreen with SPF 15 allows only 1/15 of the sun’s UV rays. What per cent of UV rays does the sunscreen abort?
2. Suppose a sunscreen allows 25% of the sun’s UV rays.
a. What fraction of UV rays does this sunscreen block? Give your answer in lowest terms.
b. Use your answer from Part (a) to calculate this sunscreen’s SPF.
Explain how you found your answer.
3. A label on a sunscreen with SPF 30 claims that the sunscreen blocks about 97% of harmful UV rays. Assuming the SPF factor is accurate,
is this claim true? Explain
For an amount, explain why, a 20% increase followed by a 20%
decrease is less than the original amount
Living on your own: Sanjay is looking for one-bedroom appartment
on rent. At Neelgiri appartments, rent for the first two months is
20% off. The one bedroom rate at Neelgiri is Rs 6,000 per month. At
Savana appartments, the first month is 50% off. The one bedroom
rate at Savana appartments is Rs 7000 per month. Which appartment
will be cheaper for the first two months? By how much?
A store is having a 25% discount sale. Sheela has a Rs 50 gift voucher
and wants to use it to buy a board game marked for Rs 320. She is
not sure how to calculate the concession she will get. The sales clerk
has suggested two ways to calculate the amount payable.
– Method 1: Subtract Rs 50 from the price and take 25% off the
resulting price.
– Method 2: Take 25% off the original price and then subtract Rs 50.
a. Do you think both the methods will give the same result? If not,
predict which method will be beneficial for her.
b. For each method, calculate the amount Sheela would have to pay.
Show your work.
c. Which method do you think stores actually use? Why?
At a toy shop price of all the toys is reduced to 66% of the original
price.
(a) What is the sale price of a toy that originally costs Rs 90?
(b) How much money would you save on a toy costing Rs 90?
Store A and Store B both charge Rs 750 for a video game. This week
the video game is on sale for Rs 600 at Store B and for 25% off at
Store A. At which store is the game less expensive?
The following items are purchased from showroom:
T-Shirt worth Rs 1200.
Jeans worth Rs 1000.
2 Skirts worth Rs 1350 each.
What will these items cost to Shikha if the sales tax is 7%?
Rahim borrowed Rs 10,24,000 from a bank for one year. If the bank
charges interest of 5% per annum, compounded half-yearly, what
amount will he have to pay after the given time period. Also, find the
interest paid by him.
Brinda purchased 18 coats at the rate of Rs 1,500 each and sold
them at a profit of 6%. If customer is to pay sales tax at the rate of
4%, how much will one coat cost to the customer and what will be
the total profit earned by Brinda after selling all coats?
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