- Option : C
- Explanation : When A runs 5 rounds, B runs 4 rounds (ratio of speeds)

A passes B each time A has run 5 rounds or 5 x 1/4 = 5/4km. = 1 1/4km

1 1/4km is contained in 4 km 3 times. Hence A passes B thrice.

- Option : D
- Explanation :

Total area to be painted

= 10 x 15 (ceiling) + 2 x 10 x 10 (wall) + 2 x 10 x 15 (wall)

= 650 sq.ft

In one day Meera can paint 10 x 10/2 = 50 sq ft

Ashok can paint 10 x 10/3 = 100/3 sq ft,

So, together they can paint 250/3 sq ft per day.

Let number of days Ashok works be x.

Work done in 9 days = 50(9 - x) + (250/3)x = 650

∴ 450 - 50x + (250x/3) = 650

⇒ 250x/3 = 200

⇒ x = 6 days.

- Option : C
- Explanation :

Let pipe B alone take b hours longer than if both A and B were open.

8 = √(4 × x)

⇒ 64 = 4 × x

⇒ x = 16 hours.

Alternatively

Part filled if both A and B are open = 1/8

Part filled if only A is open = 1/12

∴ Part filled if only B is open = (1/8) - (1/12) = 1/24

∴ B alone would take 24 hours, i.e., B alone would take 24 - 8 = 16 hours longer to fill the tank.

- Option : C
- Explanation :

Top tap is operational till 18 litres is drawn out.

∴ Time after which the lower tap is usually open = 18 x 6 = 108 minutes.

∴ Time after which it is open now = 108 - 24 = 84 minutes.

∴ Litres d rawn = 84/16 = 14 litres

∴ 18 - 14 = 4 litres

were drawn by the new assistant.

∴ Time = 4 x 4 = 16 minutes.**Alternatively**

Upper tap was not used for 24 minutes.

∴ Litres drawn = 24/6 = 4 litres.

∴ Beer was drawn for 4x 4 = 16 minutes.