If you're tired of many of the calculations you need in your daily life, download and solve a percentage calculator.

Percentage calculator that calculates a percentage of the total value
A rate-of-change calculator that calculates the rate of increase or decrease of the total value.
Discount rate calculator that calculates the discount rate for a cost
-Tip calculator that calculates the cost of each person from the total price plus tip percentage of consumption
-Sales margin calculator that adds a margin to your sales

These various calculators are included in one app, "Percent Calculator."