Simple Estimation
Class 6 Maths · Chapter 3: Number Play · NCERT Ganita Prakash section 3.11
Learn
Sometimes an estimate is enough. Meher's class has sections of 41, 38 and 43 children: about 120. With 4 classes like that, her school has about 480 children.
≈ 120 × 4 = 480
Round the numbers first to estimate quickly: 4,987 + 3,112 is about 5,000 + 3,000 = 8,000.
4,987 + 3,112 ≈ 8,000
Estimates help us catch mistakes. Kabir says he watched 20,000 hours of TV last year. But a whole year has only 365 × 24 = 8,760 hours! So his number cannot be right.
365 × 24 = 8,760
Explore: estimate first, then place your estimate on the number line.
- About how much is 4,987 + 3,112? Place your estimate.
- About how much is 2,045 + 5,960?
- Each class has three sections of 41, 38 and 43 children. About how many children are in 4 such classes? (Think: about 120 per class.)
Remember
- Estimate by rounding numbers to easy values, then calculate.
- An estimate helps you check whether an answer makes sense.
Quick check
About how many children are in three sections of 31, 28 and 33?
- about 30
- about 90
- about 300
- about 900
Answer
about 90. Each is about 30, and 3 × 30 = 90.
Think about it
Estimate how many times you blink in an hour.
One answer
About 15 blinks a minute × 60 minutes is about 900 blinks an hour. A slightly different answer is fine: it is an estimate.
Practice
Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.