Question

I f the mean of 5 observation is 15 and four of them are 11, 12, 19, 20. what is the fifth number

Answer 1

13

Explanation:

the mean is calculated as

mean =
`(sum)/(count)`

let x be the fifth number , then

`(11+12+19+20+x)/(5)` = 15

`(62+x)/(5)` = 15 ( multiply both sides by 5 to clear the fraction )

62 + x = 75 ( subtract 62 from both sides )

x = 13

Answer 2

13

Explanation:

11 * 12 * 19 * 20 * 13 = 75

75/5 = 15