🧮 Adding and Subtracting Large Numbers

What your child will learn

• Students will be able to add two numbers up to 1,00,000 using the standard algorithm with regrouping.
• Students will be able to subtract two numbers up to 1,00,000 using the standard algorithm with regrouping.
• Students will be able to estimate sums and differences by rounding to the nearest 10, 100, or 1000.
• Students will be able to solve two-step word problems involving addition and subtraction of large numbers.

Lessons in this unit

1. Adding with regrouping: Add numbers up to 1,00,000 using the standard algorithm, regrouping from ones to ten lakhs as needed. Use place value charts and base-10 blocks to show why regrouping works.
2. Subtracting with regrouping: Subtract numbers up to 1,00,000 using the standard algorithm, including cases with zeros in the minuend. Use place value charts and base-10 blocks to show regrouping.
3. Estimating sums and differences: Round numbers to the nearest 10, 100, or 1000 and use the rounded numbers to estimate sums and differences. Use estimates to check if exact answers are reasonable.
4. Two-step word problems: Solve word problems that require two operations (add then subtract, subtract then add, etc.) with numbers up to 1,00,000. Use bar models to represent the problem and check answers with estimation.

Key words

regroup

To trade 10 ones for 1 ten, or 10 tens for 1 hundred, and so on, when adding or subtracting.

sum

The answer you get when you add two numbers.

difference

The answer you get when you subtract one number from another.

estimate

To find a close answer without calculating exactly, often by rounding.

round

To change a number to a nearby easier number, like 48 to 50.

two-step problem

A problem where you need to do two operations, like add then subtract, to find the answer.

Help your child at home

What to watch for

When adding, you can add from left to right without regrouping.

Help: Always start from the ones column. Regrouping changes the next column, so you must go right to left.

When subtracting across zeros, you can just 'borrow' from the zero directly.

Help: You must regroup from the first non-zero digit to the left, turning the zero into 10.

Rounding to the nearest 1000 means changing every digit to zero except the thousands digit.

Help: Look at the hundreds digit. If it is 5 or more, round up; if less than 5, round down.

You can add or subtract in any order in a two-step problem.

Help: Read the problem carefully. The order of the steps is given by the story.

Try this at home

• Add 45,678 + 32,456 in columns, carrying 1 into the tens, hundreds and thousands
• Subtract 80,004 - 45,678 in columns, borrowing across the zeros
• Estimate 48,230 + 31,780 by rounding to nearest 1000
• A shop has 45,678 kg of rice. It sells 12,340 kg and then gets 5,000 kg more. How much rice now?

Quick questions to ask aloud

1. What is 45,678 + 32,456?
   Show answer

   78134. Add from the ones: 8+6=14, write 4 carry 1. Tens: 7+5+1=13, write 3 carry 1. Hundreds: 6+4+1=11, write 1 carry 1. Thousands: 5+2+1=8. Ten-thousands: 4+3=7. So 78,134.
2. True or false: 70,050 - 23,456 = 46,594
   Show answer

   True. Regroup: 70,050 becomes 69,950 + 10 ones. Subtract: 10-6=4, 5-5=0, 9-4=5, 9-3=6, 6-2=4. So 46,594.
3. Round 48,230 to the nearest 1000.
   Show answer

   48000. The hundreds digit is 2, which is less than 5, so we round down. 48,230 is closer to 48,000 than 49,000.

Parent guide: how to help your child with Class 5 Maths

Frequently asked questions

What will my child learn in "Adding and Subtracting Large Numbers" (Class 5 Maths)?

Your child will be able to: add two numbers up to 1,00,000 using the standard algorithm with regrouping.; subtract two numbers up to 1,00,000 using the standard algorithm with regrouping.; estimate sums and differences by rounding to the nearest 10, 100, or 1000.; solve two-step word problems involving addition and subtraction of large numbers..

How does MangoMindz teach "Adding and Subtracting Large Numbers"?

In 4 short parts (Adding with regrouping, Subtracting with regrouping, Estimating sums and differences, Two-step word problems). Each part has a picture-based lesson read aloud by Mango Teacher, a quick check, and a quiz built from common mistakes children make, with Mango, a study buddy, for questions.

How long does "Adding and Subtracting Large Numbers" take?

About 120 minutes in total, spread over 4 parts of 15–25 minutes each.

How can I help my child with "Adding and Subtracting Large Numbers" at home?

Work through a small example together, such as: Add 45,678 + 32,456 in columns, carrying 1 into the tens, hundreds and thousands; Subtract 80,004 - 45,678 in columns, borrowing across the zeros. Then ask a quick question aloud: What is 45,678 + 32,456?

What mistakes do children often make in "Adding and Subtracting Large Numbers"?

When adding, you can add from left to right without regrouping. Fix: Always start from the ones column. Regrouping changes the next column, so you must go right to left. When subtracting across zeros, you can just 'borrow' from the zero directly. Fix: You must regroup from the first non-zero digit to the left, turning the zero into 10. Rounding to the nearest 1000 means changing every digit to zero except the thousands digit. Fix: Look at the hundreds digit. If it is 5 or more, round up; if less than 5, round down.

Is "Adding and Subtracting Large Numbers" free on MangoMindz?

Yes. Every lesson part and quiz in "Adding and Subtracting Large Numbers" is free on MangoMindz, with no ads.