Sec. 4 Percentages Flashcards
a) How do you find x% of y?
e. g.
a) -Turn the % into a decimal/fraction.
- Multiply by 100
a) How do you find the new amount after a % inc./dec.
b) a toaster is £38 exc. VAT. VAT is charged at 20%. What is the cost inc. VAT?
a) Find the multiplier that represents the %
e. g. 5% inc. = 1+0.05= 1.05
26% dec.= 1-0.26=0.74
a) How do you express x as a % of y?
b) There are 480 pupils in a school. 55% of them are girls and 59 of them have blond hair. What % of the girs have blond hair?
a) -Divide x by y
- Multiply by 100
a) How do you find the % change?
b) How is a % change question worded?
a) Use the formula: % change= (diff/OG)x100
b) They will ask you to find % inc./profit or error or dec./ loss or discount
a) %Q: How do you find the original value?
e. g. A house dec. in price by 10.55 to £132 600. Find what it was worth before the rise.
a) How do you solve a simple interest question?
b) R invests £380 in an account which pays 3% simple interest per year. How much will she have in 4 years?
a)
- Find the interest made in one year ( Find multiplier and x by the amount)
- Multiply this by the no. of years
Working with %s questions
Working with %s questions
a) What is the formula for compound interest?
Susan buys a car for £6500
a) The car depreciates by 9% each year. How much will it be worth in 3 years?
b) How many complete years will it be before the car is worth less then £3000?
a) Use the formula: 6500(0.91)3
a) There are 360people in a village. The population has grown by 20% in the last year.
If the population continue sto grow at the same rate, how many years will it be before it doubles in size?
a) Compound interest Q: 360x2=720
1st yr: 1.2x360=432
2nd yr: 1.2x432=518.4
3rd yr: 1.2x 518.4=622.08
4th yr: 1.2x622.08x1.2=746.50
A shop keeper sells a pair of gloves for £3.70 and makes a 48% profit.
a) What is thecost price of a pair of socks/
b) The shop has a sale and has a 36% loss on socks. What is the price of the socks during the sale.
£3.70 = 1.48 (148%)
(/1.48)
£2.50 = 100%
? : Why not 1% rather than 100%
The owners of a museum are expecting a 14% inc. in visitors next year.
This year they had 20400 visitors.
How many should they expect next year>
1.14 x 20400 =23265
to 3sf + 23300
Method 2
20400x0.14= 2856
20400+2856=23265
I wish to invest $5000 for three years and have decided to go with the HR building society.
The Silver account pays 895% interest simple interest per annum.
The Gold account pays 2/.3% simple interest on the first £4000, but no additional money is invested.
How much will I earn if I choose:
a) the silver account
b) the gold account
a) silver:
Type in calc. 5000x1.895% =94.75 (amount per year0
x3=£283.25
without calc. 0.01895x5000=94.75
b) gold:
£4000x2.3%=92
x3= £276
Emma makes wooden funiture. It costs her £10 for the materials to make one chair and £7 a day to rent the workshop.
If Emma makes 4 chairs in 5 days and sells them for £120, in total wha is her profit?
Materials =4 x £10=£40 40 +35=75
Rent: 5x£7 = £35 120-75=45
Profit as a % of the money made:
profit/how much cost her 45/75=60%
Rob withdraws £340 from his bank account to pay for a telescope, making his account £242 in debit.
He then sells his telescope and deposits his takings back into his account , after which it is £176.20 in credit.
Assuming no other transactions took place during this what was Rob’s % profit on the telescope.
242+176.20= 418.20 - amount he put back into his account
418.20-340=78.20
Profit as a percentage of all the money made (% profit):
78.20/340=0.23
=23%
There are appromimately 6000 fish and chip shoops in the UK.
On average a fish and chip shop gets around 160 customers a day.
Given the population of the of the UK is around 60 million, approximately waht % of the population visit a fish and chip shop each day?
(no. of visits per day) 160 x 6000 ( no. of shops)
÷
60x106 (population)
x100 = 1.6%
Amy has 20 pets. 60% of are dogs and three of the dogs have black fur.
Without using a calculator, calc. the % of Amy’s dogs that have blac fur.
Calc no. of dogs: 20x0.6 =0.75
3/12 x 100= 25%
At a film festival there are 40 movie stars. Daniel meets 85% of them and 16 other people.
What % of the people Daniel met were’nt move stars?
Calc. the no. of movie stars
0.85x40=34
Total no of people: 34=16=50
(16/50)/100=32%
