1.) The simple interest earned in a given time varies jointly as the principal (P) and the rate (r). If 25,000.00 earned 5,250.00 at a 7% rate,how much would 18,000.00 earned at 11% at the same time?
2.)If z varies directly as the square of x and inversely as y,what happens to the value of z if x is doubled andy y is tripled?
3.) If r varies directly as s and inversely as t,how is the value of r affected if it is decreased by 25% ?

please can someone help me,solve this problem. in advance thank you~ :)



Its so hard... try to do it with your own