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
Answered by Sarah P. Maths tutor

9046 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Find the values of x for the equation: x^2 - 8x = 105


Show that ((sqrt(18)+sqrt(2))^2)/(sqrt(8)-2) can be written in the form a(b + 2) where a and b are integers.


Claire drove from Manchester to London, it took her 4 hours at an average speed of 85 km/h. Matt drove from Manchester to London, it took him 5 hours. Assuming he took the same route as Claire and took no breaks, work out his average speed in km/h.


2x^2-7x+3=0, solve the following for the two solutions of x


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences