In what time will a sum become three times itself at 20% per annum, at simple interest?

In how many years will a certain sum becomes five times itself at 20% per annum simple interest?

In what time will a sum of money double itself @ 20% per annum (p.a) simple interest ?

In how many years will a certain sum become 3 times itself at 25% per annum under simple interest? (a) 5 (b) 8 (c) 12 (d) 6

In what time will a sum of money double itself at 15% per annum?

In what time will a sum double itself at 4% per annum, at simple interest ?

What time will it take for a sum to amount to three times itself at 12% per annum under simple interest ?