Maths

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?

  1. 👍 0
  2. 👎 0
  3. 👁 138
  1. 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.

    1. 👍 0
    2. 👎 0

Respond to this Question

First Name

Your Response

Similar Questions

  1. math

    Mrs. Richmond bought some apples and pears in the ratio 3:5. After she gave away 3/5 of the apples and 40 pears, the ratio of apples to pears became 2:5. An apple costs 30 cents. A pear costs 15 cents more than an apple. How much

    asked by john on July 28, 2014
  2. word problem(algebra)

    at the market, a pear cost b cents&an apple cost 7 cents less than a pear.Mrs Ravi bought 4 pears&an apple.Find the total amount Mrs Ravi paid in terms of b. Help me!

    asked by kimi on September 24, 2011
  3. Algebra

    A phone company offers two monthly charge plans. In Plan A, the customer pays a monthly fee of $13 and then an additional 6 cents per minute of use. In Plan B, there is no monthly fee, but the customer pays 8 cents per minute of

    asked by Gilbert on September 25, 2015
  4. arithmetics

    mrs sue you answered my questions yesterday. How do you figure 8 percent of 75? on number 2 can you tell me how 1/3 of an hour is 20 minutes? number 3 how do you times 1 1/2 times $8.60 i get the 4th one thank you on the last one.

    asked by for ms sue on July 26, 2007
  1. Economics

    Elesha babysits on the weekends for extra money. Suppose that three neighbors with children are interested in paying Elesha to babysit their children. In particular, Dr. and Mrs. Brown would be willing to pay $30 to have Elesha

    asked by Cole on April 25, 2015
  2. english

    Has anyone read Kate Chopin is so could you check my answers? 1. When Mrs. Sommers leaves to go shopping, she forgets to take money. her daughter Mag’s size. her preferred store. to eat lunch.***** 2. The resolution of a story

    asked by lee on November 18, 2012
  3. Algebra / direct variations

    Select all of the following that are a direct variation. Songs are 99 cents each to download. Tickets for rides at the fair are $1 each. Arcade games are 50 cents or $1. To go tubing it is $5 to rent the tube and $7 for each hour

    asked by isaac clarke on October 17, 2014
  4. ALGEBRA

    Mae open her coin purse and found pennies,nickels and dimes with a total value of $2.85.If there are twice as many pennies as there are nickels and dimes combined.How many pennies,dimes and nickels are there if she has a

    asked by vincent on September 18, 2015
  1. health

    you are assigned to help Mrs.Smith with meals and housekeeping.Mrs smith has a large collection of tea cups.figurines and glass lamps.She wants you to dust each item separately every time you visit.this leaves no time for you to

    asked by kiki on May 13, 2015
  2. math

    a parking lot charges $1.50 for the first hour of parking and 55 cents for each additional half hour how much would it cost to park a car from 12:45pm to 6:15 pm

    asked by jim on May 13, 2014
  3. Genetics

    Both Mrs. Smith and Mrs. Jones had babies the same day in the same hospital. Mrs. Smith took home a baby girl, whom she named Shirley. Mrs. Jones took home a baby girl, whom she named Jane. Mrs. Jones began to suspect, however,

    asked by Samantha on May 8, 2019
  4. statistics

    At a local high school students were randomly assigned to one of two math teachers- Mrs smith and mrs jones. After the assignment, Mrs Smith had 30 students and mrs jones had 25 students. at the end of the year each class took the

    asked by Anonymous on March 27, 2012

You can view more similar questions or ask a new question.