Number

Question 1

How do you change a fraction to a decimal?

Answer 1

To change a fraction to a decimal you divide the top number by the bottom.

Question 2

How do you change recurring decimals to fractions?

Answer 2

Let your decimal equal x. Eg. X=0.3r .Times x by a power of 10, so the whole of the recurring sequence is on the left. 10x=3.3r. Subtract the first equation from the second, so you will be left with 9x=3. This means x=3/9, and your fraction is 1/3.

Question 3

What are upper and lower bounds?

Answer 3

They are the biggest and smallest figures a rounded figure could be. E.g. 20 to the nearest ten could be 15 to 25. With subtracting bounds to find the largest value, minus the UB of the first from the LB of the other. Do the opposite to find the smallest value.

Question 4

What is appropriate degree of accuracy?

Answer 4

It is when you round until the upper bound and lower bound are different. E.g. Two numbers are 10.8670 and 10.7912. They can both round to one sf(10), and two sf (11), but not three, as they are different there.

Question 5

What is a reciprocal?

Answer 5

The number you times a fraction by to get 1. It is the fraction, but just flipped over. So,the reciprocal of 1/7 is 7/1

Question 6

How do you do percentage increase or decrease?

Answer 6

You find the multiplier, then multiply the original price by the multiplier. E.g. A scarf of £20 is reduced by 15% in a sale. 100%-15%=85%. So the multiplier is 0.85. £20x 0.85=£17.

Question 7

How do you do compound interest and decay?

Answer 7

You do the original amount, times the increase, to the power of the number of years. E.g. £1000 is put in a bank with an annual interest of 8%. How much is there after ten years?
1000 x 1.08^10 = £2158.93

Question 8

How would you do a reverse percentage?

Answer 8

You need to find the original amount (x), so you do x=price / multiplier, to find the original price. E.g. A hat has been reduced by 15% in a sale and now costs £30.60. You do x = £30.60/ 0.85. You get £36

Question 9

How do you work out percentage change?

Answer 9

Percentage change = ((new amount - original) / original amount) x 100
A house is bought for £275,000. It now costs £31500. What is the percentage profit? (£315000-27500 / 27500 ) x 100 = 14.54%