My father

My father cut 78 slats on the fence. The shortest of them was 97 cm long, and the longer one was 102 cm long. What was the total length of the slats in cm?

Correct answer:

x =  7761 cm

Step-by-step explanation:

$$\begin{gathered} a=97\text{cm} \\ b=102\text{cm} \\ p=\frac{a+b}{2}=\frac{97+102}{2}=\frac{199}{2}=99.5\text{cm} \\ n=78 \\ x=n\cdot p=78\cdot \frac{199}{2}=\frac{78\cdot 199}{2}=\frac{15522}{2}=7761\text{cm} \end{gathered}$$

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