Tasks for interest

Consider the three main types of interest tasks.

Finding the percentage of the number

The task of the textbook "Vilenkin 5 class"

The company manufactured 500 pumps per quarter, of which 60% had the highest quality category. How many pumps of the highest quality category has the company manufactured?

Decision:

Find 60% of the 500 (total number of pumps).

60% = 0.6

500 • 0.6 = 300 pumps of the highest quality category.

Answer: 300 pumps of the highest quality category.

Finding the number of its percentage

Since the tasks “percentage by number” and “number by its percentage” are very similar and it is often not immediately clear what type of task is in front of us, try to read the text carefully. If you see the words “who”, “what constitutes” and “which constitutes”, most likely you have the task “ number by its percentage ”.

The task of the textbook "Vilenkin 5 class"

A student read 138 pages, which is 23% of all pages in a book. How many pages are in a book?

Decision:

So, we do not know how many pages in the book. But we know that the part that the student read (138 pages) is 23% of the total number of pages in the book. Since 138 pages are just a part, the number of pages will naturally be more than 138. This will help us with the check.

Check: 600> 138 (this means that 138 is part of 600).

Answer: 600 (p.) - the total number of pages in the book.

How many percent does one number make from another

The task of the textbook "Vilenkin 5 class"

Of the 200 watermelons, 16 were immature. How many percent of all watermelons were unripe watermelons?

Decision:

What is asked about? About immature watermelons. So, we divide 16 by the total number of watermelons and multiply by 100%.

Answer: 8% are immature watermelons from all watermelons.