Ways To Help You Quickly Calculate In Your Mind The Amount Of The Check And Discounts In The Store

2024 Author: Bailey Albertson | [email protected]. Last modified: 2023-12-17 12:53

How to learn to count in your head so as not to get confused in price tags and delivery in the store

The school seeks to comprehensively develop students, investing in them a huge amount of knowledge. But several years after its completion, we understand that the logarithms and valence of chemical elements were not very useful to us. But simple mathematics does not leave us for a minute, because it is not always convenient to take out the phone and turn on the calculator to calculate the amount of the check and the amount of the discount.

Percentage of the amount

When visiting a store or ordering goods on the Internet, we calculate our financial capabilities, taking into account the discounts provided. There is a very simple trick for calculating percentages.

Just divide the amount on the check by 5 - this is your discount. If the purchase costs 85 rubles, then 20% of 85 is calculated as follows: 85/5 = 17.17 rubles - the amount of your benefit. The same is with 40%. Divide the amount by 5 (you will find out 20%) and multiply by 2. 85/5 = 17, 17 x 2 = 34.34 is the value of a 40% discount from 85.

To calculate 10%, just put a comma in front of the last digit. That is, 10% of 1,568 is 156.8.

Sum of multidigit numbers

If you are buying multiple items that have multi-digit values and the addition is causing confusion, separate them into digits and add each separately.

First, we divide them into digits: 1 256 (1,000, 200, 50 and 6), 372 (300, 70 and 2). Now we add up by category: thousands (1,000 + 0), hundreds (200 + 300), tens (50 + 70) and ones (6 + 2). We get 1,000 + 500 + 120 + 8 = 1,628.

Multiply if the price tag ends in 9 or 99

Many stores confuse us with price tags that end in 9 or 99. If you buy multiple items with a similar value and want to know the total amount, multiply the number of items you buy by 10 or 100 and subtract what you added. Let's say you buy 12 candles at 99 rubles: 12 x (100 - 1) = 1,200 - 12 = 1,188.

Multiplication by 2

The same scheme will help to multiply the number ending in 9. Just add one, that is, round to tens, and subtract the number of items.

The cost of two chocolates at 139 rubles is easy to calculate as follows: (139 + 1) x 2 = (140 x 2) - 2 = 280 - 2 = 278.

Add two-digit numbers

Rounding can help you add more than just the same numbers. For example, you need to know the sum of four products with prices: 54, 79, 23 and 58. 79 and 58 we can round up to 80 (79 + 1) and 60 (58 + 2), respectively.

We get: 54 + 23+ 80 + 60 = 77 + 140 = 217. Now let's subtract the value by which we rounded up: 217 - 3 = 214. This is the required sum.

Features of subtraction

A similar method is used for subtraction. Just round up the numbers, and in the final add the amount by which they were increased.

1 565 - 57 - 29. Round 57 to 60 (50 + 3) and 29 to 30 (29 + 1). We get 1 565 - 60 - 30 = 1 505 - 30 = 1 475. Now we add the sum of the numbers by which we rounded off: 1 475 + 4 = 1 479.