% rate of interest
Harriet had `£3500` in her savings account. After a year she had `£3800`. What `%` rate of interest did she have on her account?
Multiply both sides by `x` to get `x` on its own (whatever you do to one side you do to the other).
Multiply both sides by `3800` to get `x` on its own
Divide both sides by `3500` to get `x` on its own
After a year Harriet had `108.57%` of her original amount of `£3500`. Take away the original amount which is represented by `100%` to find out the rate of interest.
`108.57 - 100 = 8.57%` per annum
Answer: Harriet had `8.57%` interest rate