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.

Answered by Sarah P. Maths tutor

8712 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

White paint costs £2.80 per litre. Blue Paint costs £3.50 per litre. White paint and blue paint are mixed in the ratio 3:2 Work out the cost of 18 litres of the mixture.


Find an equation of the straight line that is perpendicular to the straight line x + 3y = 7 and that passes through the point (4,9).


How do you solve these simultaneous equations? 4x + 5y = 8; 2x + 3y = 5


write log2(5) +log2​​​​​​​(3) in its simplest form


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences