Grade 5 · Unit 1: Number and place value

Mental addition

Large numbers and decimals in your head.

Adding prices

A shirt costs ৳649.50 and a cap ৳199.50. Adding them in your head is quick with the right strategy. 649.50 + 199.50 = 649.50 + 200 − 0.50 = 849.

Decimal complements

Know pairs that make 1: 0.3 + 0.7, 0.25 + 0.75, 0.35 + 0.65. And pairs that make 10: 6.4 + 3.6. These are decimal complements.

Partitioning decimals

Split into wholes and decimal parts. Add each part. Combine.

Large numbers

Think of 198 000 as 200 000 − 2000. Add 200 000 and subtract 2000. Answer: 543 000.

What I learnt

• I can use decimal complements.
• I can add decimals and large numbers mentally.