Rates and variations questions | form three Basic Mathematics

The number of tablets given to a patient was found to be directly proportional to the weight of the patient. If a patient with 34kg was given 9 tablets, find how many tablets would be given to a patient whose weight is 48kg.

Four people can eat 2 bags of rice each weighing 10kg in 12 days. How many people can eat 6 bags of rice of the same weight in 18 days?.

The surface area of a sphere , V mm² varies directly as the square of its diameter d mm. If the surface area is to be doubled, what ratio must the diameter be altered?

Juma sells one litre of milk at sh 600. How many litres of milk will Juma sell to get sh 208,800?.

The compression l of a spring is directly proportional to the thrust, T newtons exerted on it . If a thrust of 2 newtons produces a compression of 0.4cm, find:

1. The compression when the thrust is 5 newtons
2. The thrust when the compression is 0.7cm.

A bus travels 240km using 16 litres of diesel. How many litres of diesel are needed to drive 90km?

If y² varies directly to x-1 and inversely to x+d and if x=2 , d=4 for y=1, then find x when y=2 and d=1.

The power (P) used in an electric circuit is directly proportional to the square od the current (l). When the current is 8 Ampere (A), the power used is 640 Watts (W),

1. Write down the equation relating the power (P) and the current (l).
2. Calculate the current (l) when the circuit uses 360 watts.

If x*y is defined as , find (5*-2)*(3*-4).

The number of square tiles needed to surface the floor of a hall varies inversely as the square of the length of a side of the tile used . If 2016 tiles of the side 0.4m would be needed to surface the floor of a certain hall, how many tiles of side 0.3m would be required?.