I just wanted to check my answer for a question,
Kath places £100 pound into a bank account to save for a family holiday. Each subsequent month she increases her payments by 5%.
Assuming the bank does not pay interest, Find:
a.) The amount of money after 9 months: I got 1102.656432
b.)Show that n > log4/log1.05: I got to a stage where -1.05^n > -4 and assumed it is the same as 1.05^n > 4, then continued to use logs to show that n > log4/log1.05 or am i wrong to do that, otherwise there seems nothing else you can do, i know when you divide by a negative you flip the sign, but if divided by -1 and both sides of -1.05^n > -4 that means i would end up with 1.05^n < 4, which leads me with a wrong answer at the end.
c.)Maggie begins to save at the same time as Kath. She initially places £50 into the accountm and plant ot increaser her payments by a constant amount each month. Given that she would like to reach a total of £6000 in 29 months by how much should she increase her payment by each month? I don't know that to do for this, I had a go and got 1, don't think its right though. (Do you use part b to help here?)