percentage change

• How to work out Percentage Increase if the initial value is 60 and the final value is 90

  90-60=30 (find the difference)

  30/60=0.50 (divide by initial value)

  0.50X100=50% increase (x by 100)
• Increase £60 by 20% on a calculator and without a calculator

  Calculator No calculator

  100+20=120. 100%=60

  120/100=1.2. 20%=12

  1.2x60=£72. 60+12=£72
• Reduce 30 by 5% then 3% again.


  1)find both decimal multipliers

  100-5=95/100=0.95

  100-3=97/100=0.97

  0.97x0.95x30=27.645
• A man has to pay 20% of there 40,000 salary to taxes. How much is he left with?


  (20x40000)÷100=8000

  40,000-8000=32,000 left
• Calculate the interest on borrowing £40 for 3 years if the simple interest rate is 5% per year. (simple interest)


  First, work out the amount of interest for 1 year by working out 5% of £40, which is £2. The money is being loaned for 3 years, so multiply this amount by 3: £2×3=£6. So the amount of interest on borrowing £40 for 3 years is £6, which makes the total amount payable £46.
• what is the equation for compound interest?


  \(A = P(1 + r/n)^{nt}\)

  
• If you put £100 in an account with an annual compound interest rate of 10%, what would the money be after 2 years?


  the account will increase by 10% in year one. The new amount of money in the account will be £110. In year two the value of the money in the account will increase by 10% again. The new amount would be £121. This because we have increased £110 by 10%.  
• The population of a town increased by 9% between 2018 and 2019 The population in 2019 was 165 680 Calculate the population in 2018

  100-9=91/100=0.91x165,680=150,768
• A new phone cost £679 The value of the phone decreases at a rate of 4% per year. Work out the value of the phone at the end of 3 years

  679x0.96^3=£600.74