### Chapter 3: Introduction to Approximation

Read the article "Venus' day gets even longer as its spin slows"
http://www.bbc.co.uk/newsround/17192758

Which numbers mentioned in this article are exact figures, which are approximated figures?

1. 1)In the 1990s
2)A day
3)Six and a half minutes
4)20 kilometres

1. 1) Not exact
2) Exact
3) Exact
4) Exact

2. 1990 and 20 are the numbers that are estimated.

3. Exact numbers:
1)1990
2) 6.5 minutes
Approximated:
20km

1. sorry 1990 is approximated

2. 243.018 is exact

4. Numbers which are approximated are 1990's and 20 km away.
Numbers which are exact are 6 and a half minutes,243.018 days,

5. 1) the 1990s approximation. show the time period not the exact year
2) the venus day, 243.018 earth days. not approximate
3) 20 km away. approximated

6. 1)In the 1990s

2)243.018 Earth days.

3)six and a half minutes longer

4)some features on Venus will be 20 kilometres away

1. 1)approximated

2)not approximated

3)not approximated

4)approximated

7. exact: six and a half mins
20 kilometers
approximated: 1990s
243.018

8. Exact:243.018 Earth days
six and a half minutes

Estimated:1990s
20 km

9. 1)234.018 Earth Days->Approximation
2)A day on venus is 6 and a half minutes longer->Exact
3)20 kilometers->Approximation

10. 1) In the 1990s- Rounded off
2)243.018 Earth days.- Exact
3)Six and a half minutes- Exact
4)20 kilometres- Rounded off

11. Approximate value : 1990, 20km

Exact value : 6.5 mins, 243.018

12. 1990's ,one venusion day ,20 kilometers

1. all rounded off

13. 4)1990s->Approximation

14. 1)In the 1990s,= approx.
2) lasted 243.018 Earth days = approx.
3)six and a half minutes longer = exact
4)20 kilometres away = exact

15. In the 1990(exact)s, they worked out one Venusian day - the time for the planet to spin round once - lasted 243.018 (exact)Earth days.

But now, the European Space Agency's Venus Express orbiter shows Venus' spin is getting even slower and a day on Venus is now six and a half(exact) minutes longer.

Scientists aren't sure why.

One cause could be Venus' thick atmosphere and high winds pushing against the planet's spin.

The news is important for future missions to the planet. Scientists use this data to plan missions to the planet and choose the best spot to land a rover.

The new speed means some features on Venus will be 20 kilometres(rounded up/down) away from they were expected to be.

16. Exact numbers:
1) 243.018
2) 6.5 min

Approximated numbers:
1) 20 km
2) 1990s

17. 1)1990s:approximate
2)243.018:exact
3)once:exact
4)20km:exact

18. Exact numbers:
1) 6.5 minutes
Approximate
1)20km
2)1990

19. 1990 and 20 are the numbers that are estimated.