Estimating roots

The Maths Habit

  1. Work out 53

    125

  2. Work out ∛512

    8

  3. A cube has a volume of 1000 cm3. How long is each edge?

    10 cm

A square patio has an area of 30 m2.

Guess how long each side is.

Between 5 m and 6 m, about 5.5 m

Which two whole numbers is it between?

  1. √40

    6 and 7

  2. √90

    9 and 10

  3. ∛30

    3 and 4

  4. √5

    2 and 3

Is it closer to 6 or to 7?

√40 6

Estimate √50 to 1 decimal place.

the two square numbers either side
72 = 4982 = 64▲
50
Answer7.1

Estimate √28 to 1 decimal place.

the two square numbers either side
52 = 2562 = 36▲
28
Answer5.3

Estimate √50 to 1 decimal place.

the two square numbers either side
72 = 4982 = 64▲
50
Answer7.1

Estimate ∛70 to 1 decimal place.

the two cube numbers either side
43 = 6453 = 125▲
70
Answer4.1

Estimating roots worksheet, page 1

Answer sheet

  1. A square has an area of 75 cm². Estimate its side length to 1 decimal place.

    8.7 cm

  2. Jo says √50 is about 7.5. Is this a good estimate?

    No: 7.5² = 56.25

  1. Estimate √30 to 1 decimal place.

    5.5

  2. Estimate ∛40 to 1 decimal place.

    3.4

  3. Which is bigger, √80 or 8.8? Show how you know.

    √80: 8.82 = 77.44
Exit tickets to print