Answer:
2.7 hours
Step-by-step explanation:
Assuming that each percentage is worth the same amount of time. Then we can use the Rule of three since this is a ratio problem and we are given three values and a variable which is the amount of time that the battery lasts at 15%. This variable is represented by the letter x. To solve this we simply multiply the diagonal values and divide by the last remaining value which gives us the value of the variable like so...
100% <====> 18 hours
15% <====> x hours
(15 * 18) / 100 = 2.7 hours
Finally, we can see that 15% charge on the phone will last 2.7 hours
