Audrey meausers all 7 penciles in her pecile case and wirtes down the first 6 lengths.
11.8cm, 12.4cm , 12.5cm, 13.2cm , 13.6cm, 13.1 cm
audrey calcuates the mean length of all 7 penciles to be 13cm .
find the length of the missing pencile?

click on picture to help you

14.4cm

Step-by-step explanation:

Let the 7th length be y

Mean of the length = sum of all the length/number of let

Mean of the length = 13cm

13 = (11.8 + 12.4 + 12.5 + 13.2 + 13.6 + 13.1 + y) /7

13 = (76.6 + y) /7

Cross multiply to express in linear form

13 x 7 = 76.6 + y

91 = 76.6 + y

Collect like terms

91 — 76.6 = y

y = 14.4cm

Therefore, the 7th length is 14.4cm