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Question

Can you please tell me how can we solve the sums easily


Solution

Addition and Subtraction 1. Two-Step Addition

Many students struggle when learning to add integers of three digits or higher together, but changing the process’s steps can make it easier.

The first step is to add what’s easy. The second step is to add the rest.

Let’s say students must find the sum of 393 and 89. They should quickly see that adding 7 onto 393 will equal 400 — an easier number to work with. To balance the equation, they can then subtract 7 from 89.

Broken down, the process is:

  • 393 + 89
  • (393 + 7) + (89 – 7)
  • 400 + 82
  • 482

With this fast technique, big numbers won’t look as scary now.

2. Two-Step Subtraction

There’s a similar method for subtraction.

Remove what’s easy. Then remove what’s left.

Suppose students must find the difference of 567 and 153. Most will feel that 500 is a simpler number than 567. So, they just have to take away 67 from the minuend — 567 — and the subtrahend — 153 — before solving the equation.

Here’s the process:

  • 567 – 153
  • (567 – 67) – (153 – 67)
  • 500 – 86
  • 414

Instead of two complex numbers, students will only have to tackle one.

3. Subtracting from 1,000

You can give student confident to handle four-digit integers with this fast technique.

To subtract a number from 1,000, subtract that number’s first two digits from 9. Then, subtract the final digit from 10.

Let’s say students must solve 1,000 – 438. Here are the steps:

  • 9 – 4 = 5
  • 9 – 3 = 6
  • 10 – 8 = 2
  • 562

This also applies to 10,000, 100,000 and other integers that follow this pattern

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