Ed has 4 cards. There is a number on each card. Three of the numbers are 12, 6 and 15. The mean of the numbers is 10. What is the fourth number?
To find the mean you add all the numbers together and divide by the number of numbers. Call the fourth number x. Then we know that (12+6+15+x)/4 =10. then multiply both sides by 4 to get 12+6+15+x=40 which is 33+x=40. And subtracting 33 from 40 gives x=7. The fourth number is 7.
SP
Related Maths GCSE answers
All answers ▸Find an equation of the line which passes through the point (4,-7) and has slope 3.
HIGHER TIER a) Factorise the following equation into two bracket form: 2x^2-5x-12. b)2x^2-5x-12=0. Solve this equation to find the values of x, using your answer to part a). BONUS c) Sketch the function y=2x^2-5x-12, showing any x intercepts
Work out 416 + 49 + 274
What is completing the square and how do you do it?