Sujoy Kumar Datta

Ramu and Gannu can together complete a project in 16 days. After 7 days of working together, Ramu got sick and his efficiency dropped by 30%. They completed the work in 17 days, instead of 16 days. If Gannu had worked alone after Ramu got sick, how many days would he have taken to complete the remaining work?

Anu and Ana working together can complete a project in 20 days. They started working together, but Anu left after x days and Ana finished the remaining work in x/2 more days. Had Anu left after 2x/3 days, Ana would have taken x more days to finish the remaining work. What is the ratio of efficiency of Anu to that of Ana?

A water-tank is fitted with pipes, some filling it and others draining it. All filling pipes fill at the same rate and all draining pipes drain at the same rate. The empty tank gets filled in 6 hours if 6 filling and 5 draining pipes are used, but takes 60 hours to get filled if 5 filling and 6 draining pipes are used. In how many hours will the empty tank get filled if one draining and one filling pipe are used?

A septic tank is emptied everyday at a fixed time. Immediately after that, either pump X or pump Y or both start working until the tank is full. On Monday, X alone filled the tank at 8 pm. On Tuesday, Y alone filled the tank at 6 pm. On Wednesday, X alone worked till 5 pm, and then Y worked alone from 5 pm to 7 pm, to fill the tank. At what time will half of the tank be filled if both pumps are used together all along?

In a factory, one section produces only nuts at the rate of 100 nuts in a minute and needs to a break for 5 minutes after production of every 1000 nuts. Another section produces only bolts at the rate of 75 bolts in a minute and needs a break for 10 minutes after production of every 1500 bolts. If both sections start production at the same time, what is the minimum duration, in minutes, needed for producing 9000 pairs of nuts and bolts?

A paint plant has four tanks (E, F, G and H), each containing 1000 litres of a paint. The paint is pumped from one tank to another as follows.

From E to F @ 20 litres/minute,

From G to E @ 90 litres/minute,

From E to H @ 10 litres/minute,

From G to H @ 60 litres/minute,

From F to G @ 100 litres/minute,

From H to F @ 110 litres/minute.

Which tank gets emptied first, and how long does it take, in minutes, to get empty after pumping starts?

Abu can complete a work in 4 days. Bakar takes twice the time taken by Abu, Chunnu takes double that of Bakar, and Dabbu takes twice that of Chunnu to complete the work. They are paired in two groups of two. One pair takes two thirds the time required by the second pair to complete the work. The first pair comprises of

A string is wound on the exterior four sides of a cube of side n cm, starting at corner C and ending at corner D, can give exactly one turn (refer figure, not to scale). What is the string length?

In the figure, the circle‘s diameter is 3 cm. AB and MN are 2 diameters perpendicular to each other. CG is also perpendicular to AB such that AE:EB = 1:2, while DF is perpendicular to MN such that NL:LM = 1:2. The length, in cm, of DH is

Two concentric circles are such that the area of the outer circle is 4 times the area of the inner circle. A, B and C are three distinct points on the perimeter of the outer circle such that AB and AC are tangents to the inner circle. If the outer circle‘s area is 12 sq cm, then the area (in sq cm) of the triangle ABC will be