Homework Help: Maths

Posted by Annabella Richards on Monday, June 20, 2011 at 2:10am.

Mrs Smith pays kate for babysitting by giving her 10 cents for the first-half hour, 20 cents for the second half-hour, 40 cents for the third half-hour etc. How long does she work to earn $12.70?

Maths - Henry, Monday, June 20, 2011 at 4:20pm
1st half-hr = 10 cents = 5*2^1.

2nd half-hr = 20 cents = 5*2^2.

3rd half-hr = 40 cents = 5*2^3.

t = 5*2^n = 1270 cents.
5*2^n = 1270,
Divide both sides by 5:
2^n = 254,
nlog2 = log254,
n = log254 / log2 = 7.99 half-hrs =
3.99 hrs or 4 hrs.

Answer this Question

Related Questions

Math - Together these two turkeys weigh twenty pounds," said the butcher. ...
math !!!! :O - Emily’s dad pays her for picking strawberries. Each hour she...
Economics - V pays 20 cents V sells to W for 35 cents W sells to X for 55 cents ...
Macroeconomics - V pays 20 cents V sells to W for 35 cents W sells to X for 55 ...
2nd grade Math - Wich 3 flowers add up to 85 cents? Tulip-48 cents Rose-52 cents...
math !!!! :O - The cost of making money varies form coin to coin: Pennies: 0.8 ...
Algebra - How can algebra be used to solve this problem? The boy solved 10 ...
maths. - Alice spent some money on 60 stamps of two different values. The values...
Math - A plumber makes $4.50 per hour more than his apprentice. During an 8-hour...
Algebra - A long-distance call using DEC costs 20 cents for the first minute and...

For Further Reading

First Name:
School Subject:
Answer: