Final answer:
To calculate the percentage of the next phones that are working, divide the number of phones that are working by the total number of phones and multiply by 100.
Step-by-step explanation:
To calculate the percentage of the next 50 phones that are working, we first need to know how many of the previous 500 phones were working. Let's assume that 425 of the previous 500 phones were working. So the percentage of the next 50 phones that are working would be (425/500) * 100 = 85%.
Similarly, if the percentage of the previous 500 phones that were working is 435/500 * 100 = 87%, then the percentage of the next 100 phones that are working would be (435/500) * 100 = 87%.
Finally, if the percentage of the previous 500 phones that were working is 440/500 * 100 = 88%, then the percentage of the next 500 phones that are working would be (440/500) * 100 = 88%.