Better spelling

Weekly Problem 12 - 2010
Can Emily increase her average test score to more than $80$%? Find out how many more tests she must take to do so.
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

Problem



In Emily's first spelling test, she scored 1 mark out of 5, so she decided to work really hard to improve her scores.

If she scores full marks (5 out of 5) in all her tests after the first, how many more tests does she need to take, in order to increase her average to more than $80$%?

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.