Finding out a percentage of a number
say you were asked to find 85% of 65, you could find out:
- 10% = 6.5
- 80% = 52
- 5% = 3.25
so 52 + 3.25 = 55.25
or alternatively, you could simply:
65 * 0.85 = 55.25
to increase a number, say 40 by 20%, you could find:
- 10% = 4
- 20% = 8
- 40 + 8 = 48
or alternatively, you could:
40 * 1.2 = 48
remember when increasing by 5% for example, you must type in 40 * 1.05!
and remember at the end of a question, if the answer is the percentage, don't leave it as the decimal :)
compound interest is a little different.
if you earn 2% compound interest each year then the amount increases a little bit each time because after the 1st year you would take 2% of the whole amount (including last year's interest).
an easy way to solving this is:
£125 in the bank increases by 6% compound interest for 5 years.
125 * 1.06^5
1.06 is the percentage increase and the number acting as the indices is the number of years.