Estimating

Estimating

Understanding Estimation and Rounding

  • Estimation is a mathematical method used to make a rough or approximate calculation or judgement.
  • Rounding is a form of estimation that involves reducing the number of digits in a number while trying to keep its value similar. For example, 4.67 can be rounded to 5.
  • The process of rounding depends on the place value. For example, if you round to the nearest ten, you look at the unit’s place.

Rounding to the Nearest Ten, Hundred, Thousand etc

  • If you’re rounding to the nearest ten and the unit’s place digit is 5 or greater, round up. If it’s less than 5, round down.
  • The same principle applies when rounding to the nearest hundred, thousand and so on, but you check the tens place for rounding to the nearest hundred, the hundreds place for rounding to the nearest thousand, and so forth.

Estimating Sums, Differences, Products and Quotients

  • Estimation can be used to get a rough idea of sums, differences, products and quotients.
  • To estimate a sum or difference, round the numbers first, then add or subtract.
  • To estimate a product or a quotient, round the numbers first, then multiply or divide.

Practice Problems

  • Problem: Estimate the sum of 432 and 678 by rounding each number to the nearest hundred.
    • Solution: 400 + 700 = 1100
  • Problem: Estimate the product of 56 and 89 by rounding each number to the nearest ten.
    • Solution: 60 x 90 = 5400
  • Problem: Round 8997 to the nearest thousand.
    • Solution: 9000

Final Notes

  • Estimation is a crucial skill, not only for the maths classroom but also for real-world scenarios, so always understand the reasoning behind it.
  • Practise a variety of problems to get accustomed to different types of rounding and estimating.
  • It is important to remember that an estimate is not an exact answer but rather an approximation. Therefore, the actual answer may be slightly higher or lower.