1^st Method:

Let rate is R%.
Now,
P = 100;
A = 400;
I = 400-100 = 300;
Time, T = 10 years;
I = PTR/100;
Or, R = (100*I)/PT;
Or, R = (100*300)/(100*10);
Hence, R = 30%;

2^nd Method:

Here, the sum becomes 4 times that means 100, become 400;
Rate of such question is given by;
R= interest/time = 300/10 = 30%;

3^rd Method:

Here, 300% of rise in the sum,so
100——300%↑—-400;
R=(total percentage rise/given time) = 300% /10 = 30%.