Chapter 7 Decimals Worksheet - New Century Maths Page 11
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38Working mathematically
Applying strategies and reflecting: Decimal distances
Equipment: A tape measure and some coloured chalk.
Step 1: Form a group of three or four students and find a flat area such as a path,
basketball court, or the classroom floor.
Step 2: Mark a starting point on your flat area.
Step 3: Choose a distance between 1 and 4 metres, for example 3.25 m.
Step 4: Using chalk, take turns to mark your estimate of 3.25 m from the starting
point. Measure the exact length and mark it with an X.
Step 5: Give points to each person. Score 5 points for best estimate, 3 points for next
best, 2 points for next and 1 point for next.
Take turns to choose distances, and play the game until someone reaches 20 points
and wins.
Sample score sheet for one person:
Trial
Distance
Guess
Points
1
3.25
2.57
2
4.50
3.16
3
3.50
3.41
4
1.75
1.82
5
2.20
2.38
Total
Skillbank 7
Estimating answers
SkillTest
A quick way of estimating the answer to a calculation is to round each number in the
7-01
calculation.
Estimation
1 Examine these examples:
a 631 + 280 + 51 + 43 + 96 ≈ 600 + 300 + 50 + 40 + 100
= (600 + 300 + 100) + (50 + 40)
= 1000 + 90
= 1090
(Actual answer = 1101)
b 55 + 132 − 34 + 17 − 78 ≈ 60 + 130 − 30 + 20 − 80
= (60 + 20 − 80) + (130 − 30)
= 0 + 100
= 100
(Actual answer = 92)
c 67 × 13 ≈ 70 × 12
= 840
(Actual answer = 871)
d 78 × 7 ≈ 80 × 7
= 560
(Actual answer = 546)
208
NEW CENTURY MATHS 7
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