Question

On his last four tests, danilo scored 55%, 78%, 84%, and 93%.what score should he get on the next test so that his average on all five tests is 80%?

Answer 1

`\\ \text{On his last four tests, Danilo scored }55\%, \ 78\%, \ 84\% \text{ and }93\%\\ \text{Let the score in the next test is x percent.}\\ \\ \text{now given that the average of all five tests is }80\%\\ \\ \text{so we have}\\ \\ (55+78+84+93+x)/(5)=80\\ \\ \Rightarrow (310+x)/(5)=80\\ \\ \text{now on cross multiplying, we get}\\ \\ 310+x=80* 5\\ \\ \Rightarrow 310+x=400\\ \\ \Rightarrow x=400-310\\ \\ \Rightarrow x=90`

Hence Danilo should score 90 % in the fifth test to get an average of 80%