Need help with a math questions

Question

If james is starting to save $150 to buy a new cell phone. In January he saved $5. In February he saved twice as much as he saved in January for a total of $15. If James continues to save twice as much each month as he saved the previous month, in which month will his totals savings be enough to buy the phone?

Answer 1

Answer 2

If you are saving for a $150 cellphone and you start with $5 in Jan and $15 in Feb, you will have $155 in May. In Feb you doubled the amount saved in Jan. In Feb, you set aside $10 in March, $20, in April, $40, and in May $80. You add the amount saved for the months with $15 earned from Feb.