Average Test-6 (Calculating average Speed)

Answer: Option C

Explanation

According to the question

We know the formula

Average speed of the train=$\frac{2\mathrm{AB}}{\mathrm{A}+\mathrm{B}}$

where A=25 and B is to determine

$$\begin{gathered} = 24=\frac{2\times 25\times \mathrm{B}}{25+\mathrm{B}} \\ = 12=\frac{25\mathrm{B}}{25+\mathrm{B}} \end{gathered}$$

= 300+12B=25B

=300=13B

(Or) B=$\frac{300}{13}=23\frac{1}{13}\mathrm{km}/\mathrm{hr}$

Hence, Option C is correct.

Answer: Option B

Explanation

Distance between Rajpur and Somgarh

= Average speed×Time

=$\frac{69\times 35}{60} \mathrm{km} =\frac{161}{4} \mathrm{km}$

New speed =(69+36) Km/hr

 = 105 km/hr

$$\begin{gathered} \mathrm{Time} =\frac{\mathrm{Distance}}{\mathrm{time}}=\frac{161}{4\times 105}\mathrm{h} \\ =\frac{161\times 60}{4\times 105}\min \\ = 23 \min \end{gathered}$$

Hence, Option B is correct.

Answer: Option C

Explanation

According to the question

We know the formula,

Average speed= $\frac{2\mathrm{AB}}{\mathrm{A}+\mathrm{B}}$

$$\begin{gathered} =\frac{2\times 58\times 52}{58+52} \\ =\frac{6032}{110} \end{gathered}$$

= 54.83

= 55 km/hr (approximate)

Hence, Option C is correct.

Answer: Option A

Explanation

Given,

A=25 km/hr, B=40 km/hr

We know the formula,

Average speed= $\frac{2\mathrm{AB}}{\mathrm{A}+\mathrm{B}}$

∴ Required average speed

$$\begin{gathered} =\frac{2\times 25\times 40}{25+40} \\ =\frac{2000}{65} \end{gathered}$$

= 30.76 km/hr

Hence, Option A is correct.

Answer: Option C

Explanation

According to the question,

A=30 km/h, B=15 km/h, C=10 km/h

we know the formula,

Average speed= $\frac{3\mathrm{ABC}}{\text{AB+BC+CD}}$

∴ Required average speed

$$\begin{gathered} = \frac{3\times 30\times 15\times 10}{30\times 15+15\times 10+10\times 30} \\ =\frac{13500}{900} \end{gathered}$$

 = 15 km/h

Hence, Option C is correct.