Literal Equations and Rearranging Formulae
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Literal Equations and Rearranging Formulae — Free MYP5 Mathematics (Standard) Practice Questions

1QuestionRearranging with Fractions and BracketsAssessment Practice
2 marks~3 minCriterion A
A surveyor models a triangular plot of land. The three sides measure a=5a = 5 m, b=7b = 7 m, and c=6c = 6 m, where angle θ\theta is opposite side cc. The cosine rule states:

c2=a2+b2−2abcos⁡θc^2 = a^2 + b^2 - 2ab\cos\theta
a
Rearrange the cosine rule to make cos⁡θ\cos\theta the subject. [1]
b
Calculate θ\theta and hence justify whether the triangular plot contains any obtuse angle. [1]
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Solutions

2QuestionCommon Mistakes in RearrangingAssessment Practice
2 marks~3 minCriterion C
A landscape architect is designing a triangular garden bed. The area must be exactly 30 m230\ \text{m}^2 and the base measures 6 m6\ \text{m}.

To find the required height hh, a student rearranges A=12bhA = \frac{1}{2}bh and writes:

h=12×30×6h = \frac{1}{2} \times 30 \times 6
a
Identify the error in the student's rearrangement. [1]
b
Deduce the correct value of hh. [1]
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Solutions

3QuestionApplications in Geometry and Physics FormulasAssessment Practice
4 marks~6 minCriterion D
A photographer uses a thin lens with a focal length of f=50f = 50 mm. The lens formula

1f=1u+1v\frac{1}{f} = \frac{1}{u} + \frac{1}{v}

relates object distance uu and image distance vv.
a
Show that v=ufu−fv = \dfrac{uf}{u - f}. [1]
b
An object is placed at u=200u = 200 mm from the lens. Calculate the image distance vv. [1]
c
A sharp image requires vv to fall within 2 mm of the calculated value. Assess whether the thin-lens model is reliable enough to guarantee this precision for a professional camera lens, justifying your answer with two distinct physical limitations of the model. [2]
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Solutions

4QuestionApplications in Geometry and Physics FormulasAssessment Practice
4 marks~6 minCriterion B
A construction team is checking whether a triangular brace is truly right-angled before installing it. They measure the three sides as 2.5 m, 6 m, and 6.5 m.

Before applying this to the brace, investigate the relationship between side lengths in right triangles using the four Pythagorean triples below.

Triangle 1: (3,4,5)(3, 4, 5) — Triangle 2: (5,12,13)(5, 12, 13) — Triangle 3: (6,8,10)(6, 8, 10) — Triangle 4: (7,24,25)(7, 24, 25)
a
For each triangle, calculate the sum of the squares of the two shorter sides and the square of the longest side. [1]
b
Deduce a general equation relating the three side lengths of any right triangle. [1]
c
Using your equation from (b), advise the construction team whether the brace with sides 2.5 m, 6 m, and 6.5 m should be approved for installation, justifying your answer with full working. [2]

Solutions

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