Transcript Carpentry & Joinery Phase 4 Maths Ratio & Proportion Sample Questions & Solutions Carpentry & Joinery Phase 4 Maths Ratio & Proportion • A pitched roof is constructed.

Carpentry & Joinery
Phase 4 Maths
Ratio & Proportion
Sample Questions &
Solutions
Carpentry & Joinery
Phase 4 Maths
Ratio & Proportion
• A pitched roof is constructed with a pitch
of 1 : 3 rise to span ratio. If the span of
the roof is 4.8m, what is its rise
• 4.8 is = 3 parts so 4.8 ÷ 3 = 1.6 or 1 part
• 1.6 m = rise
• Or the rise is = 1/3 of the span = 1.6 m
rise?
4.8m
Carpentry & Joinery
Phase 4 Maths
Ratio & Proportion
• Flat roofs have a fall that does not
exceed 1 : 6 ratio of rise to run of falling
surface ( 10° pitch approx.)
• e.g. A flat roof extends from the rear wall
of a house over an extension that is 4.2m
further out. Calculate the rise given a
ratio of 1 : 9
• 4.2 ÷ 9 = 0.46m
• = 460 mm rise Answer
Carpentry & Joinery
Phase 4 Maths
Ratio & Proportion
• The recommended fall for 100mm PVC drainage
pipe from a domestic dwelling is 1 : 40
• On a run of 7.685m of 100mm waste pipe, by
how much will the pipe fall from highest to
lowest point assuming a 1 :40 gradient?
• 7.685 ÷ 40 = 0.192125 = 192mm Answer
Carpentry & Joinery
Phase 4 Maths
Ratio & Proportion
• If the cost of a carpentry project came to
a total of €7,850, calculate the cost of
each item listed when the ratio is as
follows:
1.Materials cost 2/5
2.Labour costs 3/10
3.Profit cost
1/10
4.VAT cost
1/5
Carpentry & Joinery
Phase 4 Maths
Ratio & Proportion
• Firstly, convert all fractions to the same
denominator i.e. 2/5 to 4/10 & 1/5 to 2/10
• Now we can divide our total by the
denominator (10) so 7,850 ÷ 10 = 785
• Material = 2/5 = 4/10 = 4 x 785 = €3,140
• Labour = 3/10 = 3 x 785 = €2,355
• Profit = 1/10 = 1 x 785 = €785
• VAT = 1/5 = 2/10 = 2 x 785 = €1,570
• 3,140 + 2,355 + 785 + 1,570 = €7,850