LO Round numbers RAG

Key Words: Decimal Place, Significant Figure. 19 Apr 2023

Starter Activity

Think pair share

I have £240

I want to buy 13 tickets to a pop concert. The tickets cost £15.50 each.Without working out the exact cost how can I quickly decide if I have enough money?

Mini white boards ready…Get ready to round numbers to the nearest:10, 100, 1000, to 1, 2 or 3 decimal places to 1, 2 and 3 significant figures.

7656.548

5243.568

1657.899

0.0000456

Support Task

Round these numbers to the nearest 10 and position them to the nearest 10 on the number line below.

27 31 45 58 67 99 5 3 17

Round these numbers to the nearest 100 and position them to the nearest 10 on the number line below.

271 31 456 589 670 990 525 345 79

Round these numbers to the nearest 100 and position them to the nearest 10 on the number line below.

2711 316 4567 5890 6720 9190 5325 3445 7981

Main Task

JillTick one answer and

trash the other.Rounding

Jack

3.5 (1dp) 3.56 to 1 dp 3.6 (1dp)

0.4 0.416 to 1 dp 0.4 (1dp)

0.41 (2dp) 0.416 to 2 dp 0.42 (2dp)

5.79 (2dp) 5.799 to 2 dp 5.8 (2dp)

4 (1sf) 3.56 to 1 s.f. 3.6 (1sf)

0 (1sf) 0.416 to 1 s.f 0.4 (1sf)

0.42 (2sf) 0.416 to 2 s.f. 0.4 (2sf)

5.8 (2sf) 5.799 to 2 s.f. 5.79 (2sf)

Main Task

Extension Task

Mini white boards ready…

Choose one of the three questions to answer. You must explain your answer.

PlenaryQuestion A

Give me a number that is 6 000 when rounded to the nearest1 000.

Questions B

What is the smallest number that is rounded to 61.5 whenrounded to one decimal place?

Question C

What is the largest number that is rounded to 700 whenrounded to the one significant figure?