At the end of the first month, she has saved $5.00
She is planning to add to her account an amount that is equal to the amount in the account.
a.
If she saved the first month $5.00
The second month she will save 2*$5.00 = $10.00
In the third month, she will save 2*$10.00= $20.00
In the fourth month, she will save 2*$20.00= 40.00
in the fifth month, she will save 2*$40.00 = $80.00
b. Now, we need to continue until the account amount is equal to $400.
Then:
Sixth month 2*$80.00 = $160.00
Seventh month 2*160.00= $320
Eighth month 2*$320 = $640
Hecen, at the end of the eight-month she will have enough money to buy the new bike.