Model 2 Vehicles in x/y of its usual speed Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (b)

$4/3$ × usual time - usual time = 2

$1/3$ usual time = 2

Usual time = 2 × 3 = 6 hours

Using Rule 8,

Here, $\text"A"/ \text"B"= 3/4$, time= 2 hrs.

Usual Speed

= $\text"A"/\text"Diff of A and B"$ × time

= $3/{(4 - 3)} × 2$ = 6 hours

Answer: (c)

$4/3$ of usual time

= Usual time + 20 minutes

$1/3$ of usual time = 20 minutes

Usual time = 20 × 3 = 60 minutes

Using Rule 8,

Here, A = 3, B= 4, t = 20 minutes

Usual time taken

= $\text"A"/\text"Diff of A and B"$ × time

= $3/{(4 - 3)} × 20$ = 60 minutes

Answer: (d)

Time and speed are inversely proportional.

$7/6$ × Usual time - Usual time = 25 minutes

Usual time $(7/6 -1)$

= 25 minutes

Usual time × $1/6$

= 25 minutes

Usual time = 25 × 6

= 150 minutes

= 2 hours 30 minutes

Using Rule 8,

Here, A = 6, B = 7, t = $25/60 = 5/12$ hrs.

Usual time = $\text"A"/\text"Diff of A and B"$ × time

= $6/{(7 - 6)} × 5/12 = 5/2$ hrs.

= 2 hours 30 minutes

Answer: (c)

1 m/sec = $18/5$ kmph

20 m/sec = ${20 × 18}/5$

= 72 kmph

Answer: (d)

Time and speed are inversely proportional.

$4/3$ of usual time –usual time = $3/2$

$1/3$ usual time = $3/2$

Usual time = ${3 × 3}/2$

$9/2 = 4{1}/2$ hours

Using Rule 8,

Here, A = 3, B = 4, t= $3/2$

Usual time = $\text"A"/\text"Diff of A and B"$ × time

= $3/{(4 - 3)} × 3/2 = 4{1}/2$ hrs.

Answer: (c)

Total distance

= 7 × 4 = 28 km.

Total time

= $(7/10 + 7/20 + 7/30 + 7/60)$ hours

= $({42 + 21 + 14 + 7}/60)$ hours

= $84/60$ hours = $7/5$ hours

Average speed

= $\text"Total distance"/ \text"Total time" = (28/{7/5})$ kmph

= ${28 × 5}/7$ = 20 kmph