Find the average of first 10 multiples of 7

Answer: Option B

Explanation:

$$\begin{aligned} \frac{(55 \times 50) +(60 \times 55) +(45 \times 60) }{55 + 60 + 45} \end{aligned}$$

$$\begin{aligned} \frac{8750}{160} = 54.68 \end{aligned}$$

Answer: Option C

Explanation:

$$\begin{aligned} = \frac {7(1+2+3+...+10)}{10} \end{aligned}$$

$$\begin{aligned} = \frac {7(10(10+1))}{10 \times 2} \end{aligned}$$

$$\begin{aligned} = \frac {7(110)}{10 \times 2} = 38.5 \end{aligned}$$

Answer: Option B

Explanation:

Average speed will be

$$\begin{aligned} \frac{2xy}{x+y} km/hr = \frac{2(50)(30)}{50+30} km/hr \end{aligned}$$

= 37.5 km/hr

Answer: Option C

Explanation:

$$\begin{aligned} = \frac{(38.9 \times 10)-(42 \times 6)}{4} \end{aligned}$$

$$\begin{aligned} = \frac{(1216 - 750)}{4} = 34.25 \end{aligned}$$

Answer: Option B

Explanation:

$$\begin{aligned} ( \frac {65+67+76+82+85}{5} ) = 75 \end{aligned}$$