Mentally add and subtract numbers ending in zeroes

Key notes :

🔢 Numbers ending in zeroes are multiples of 10, 100, or 1000

Examples:

  • 20, 40, 70 (tens)
  • 100, 300, 900 (hundreds)
  • 1000, 2000 (thousands)

🧠 Remove the zeroes to make the numbers easier

To add or subtract quickly, ignore the zeroes first.
Example:

  • 30 + 40 → think 3 + 4 = 7, then add back the zero → 70

➕ Adding numbers ending in zeroes

Steps:

  1. Drop the zeroes
  2. Add the basic numbers
  3. Put back the zeroes

Examples:

  • 50 + 70 → 5 + 7 = 12 → add zero → 120
  • 200 + 300 → 2 + 3 = 5 → add two zeroes → 500

➖ Subtracting numbers ending in zeroes

Steps:

  1. Ignore the zeroes
  2. Subtract the small numbers
  3. Put the zeroes back

Examples:

  • 90 − 40 → 9 − 4 = 5 → add zero → 50
  • 600 − 200 → 6 − 2 = 4 → add two zeroes → 400

🎯 Use place value (tens, hundreds) to think quickly

  • 30 means 3 tens
  • 400 means 4 hundreds

So,

  • 3 tens + 5 tens = 8 tens → 80
  • 7 hundreds − 2 hundreds = 5 hundreds → 500

⚡ Mental math tip

  • Think in tens: 60 + 30 = 6 tens + 3 tens = 9 tens = 90
  • Think in hundreds: 800 − 300 = 8 hundreds − 3 hundreds = 500

🌈 Real-life connection

  • ₹50 + ₹20 = ₹70
  • 300 ml − 100 ml = 200 ml
  • 40 minutes + 20 minutes = 60 minutes (1 hour)

🧩 Practice makes you faster!

Try quick examples:

  • 70 + 80 = ?
  • 900 − 200 = ?
  • 40 + 30 = ?
  • 600 + 300 = ?

Learn with an example

✈️ Add: 2,000 + 4,000 =_____

  • Notice that both numbers have 3 zeroes at the end. When the number of zeroes is the same, it is easy to add. First, arrange the numbers one above the other:
  • 2000+4000=_____
  • Next, add the zeroes. Wherever there is a zero below another zero, place a zero at the bottom. This is because zero plus zero equals zero.
  • 2000+4000= 000
  • Now add the remaining digits. Two plus four is six.
  • 2000+4000= 6,000

✈️ Add: 7,000 + 1,000 =______

  • Notice that both numbers have 3 zeroes at the end. When the number of zeroes is the same, it is easy to add. First, arrange the numbers one above the other:
  • 7000+1000=____
  • Next, add the zeroes. Wherever there is a zero below another zero, place a zero at the bottom. This is because zero plus zero equals zero.
    7000+1000=000
  • Now add the remaining digits. Seven plus one is eight.
  • 7000+1000=8,000

✈️ Subtract: 90,000 – 10,000 =____________

  • Notice that both numbers have 4 zeroes at the end. When the number of zeroes is the same, it is easy to subtract. First, arrange the numbers one above the other:
  • 90000-10000=_______
  • Next, subtract the zeroes. Wherever there is a zero below another zero, place a zero at the bottom. This is because zero minus zero equals zero.
  • 90,000-10,000=0,000
  • Now subtract the remaining digits. Nine minus one is eight.
  • 90,000-10,000=80,000

Let’s practice!🖊️