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Peter, James and Samuel shared some stamps. The number of stamps Peter had was 1/3 of the number of stamps Samuel had. Samuel has twice as many stamps as James. Samuel had 30 more stamps than James. How many stamps did they have altogether?

Mathematics fractions:

Darius, Ellen and Farhan each had some marbles. They traded marbles with one another. In the 1st round, Darius gave 1/5 of his marbles to Ellen.

In the 2nd round, Ellen gave 1/4 of his marbles to Farhan.

In the 3rd round, Farhan gave 1/2 of his marbles to Darius.

Darius had 45 marbles, Ellen had 30 marbles, and Farhan had 25 marbles left in the end.

How many marbles had each of them at first?

An object of mass 100 kilograms is initially at rest on the ground. A crane lifts

the object to a height of 15 metres in 8 seconds. When the object is 15 metres

above the ground, it is moving upwards with a velocity of 0.2m/s

Calculate

(a) The total mechanical energy of the object when it is 15 metres above the

ground. 

(b) The average power of the crane.