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Solving Triangles practice questions — GCSE Maths

12 free multiple-choice problems on solving triangles, ordered to match GCSE Maths difficulty, each with a full worked solution. No account needed — and there's a fresh problem set every day.

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Problem #0537 International
Mediumtrigonometry
In , and . The circumradius equals:

Problems & worked solutions

Problem #0537 International

Problem 1 Solving Triangles

In ABC, a=6 and A=π6. The circumradius R equals:

Show answer & worked solution
  1. A. 3
  2. B. 3
  3. C. 6✓ correct
  4. D. 12

2R=asinA=61/2=12R=6.

Problem #0535 International

Problem 2 Solving Triangles

In ABC, AB=5, BC=12, AC=13. The area equals:

Show answer & worked solution
  1. A. 20
  2. B. 24
  3. C. 30✓ correct
  4. D. 60

Since 52+122=132, ABC is right-angled at B. Area =12512=30.

Problem #0538 International

Problem 3 Solving Triangles

In ABC, a=5, b=6, c=7. The inradius r is closest to:

Show answer & worked solution
  1. A. 1.4
  2. B. 1.6✓ correct
  3. C. 2.4
  4. D. 3.0

s=9. By Heron, Area =9432=6614.70. So r14.7091.63.

Problem #0536 International

Problem 4 Solving Triangles

The area of a triangle with sides 5, 6, 7 is closest to:

Show answer & worked solution
  1. A. 10
  2. B. 12
  3. C. 14.7✓ correct
  4. D. 21

s=5+6+72=9. A=9432=216=6614.70.

Problem #0534 International

Problem 5 Solving Triangles

In ABC, A=π6, B=π4, and a=4. The side b equals:

Show answer & worked solution
  1. A. 22
  2. B. 4
  3. C. 42✓ correct
  4. D. 82

4sin(π/6)=bsin(π/4)41/2=b2/28=b2/2b=822=42.

Problem #0939 US SAT

Problem 6 Solving Triangles

In a triangle, two sides have lengths 4 and 5 and the included angle is 60. The length of the third side is:

Show answer & worked solution
  1. A. 41
  2. B. 21✓ correct
  3. C. 61
  4. D. 3

c2=42+522(4)(5)cos60=16+254012=4120=21.

So c=21.

Problem #0938 US SAT

Problem 7 Solving Triangles

In a triangle, a is opposite A=30 and b is opposite B=90. If a=5, then b equals:

Show answer & worked solution
  1. A. 5
  2. B. 52
  3. C. 10✓ correct
  4. D. 53

5sin30=bsin90.

sin30=12 and sin90=1, so 51/2=b1.

b=10.

Problem #0531 International

Problem 8 Solving Triangles

A right triangle has legs 3 and 4. Its area equals:

Show answer & worked solution
  1. A. 5
  2. B. 6✓ correct
  3. C. 7
  4. D. 12

Area =1234=6.

Problem #0532 International

Problem 9 Solving Triangles

In ABC, AB=6, AC=8, and A=π6. The area equals:

Show answer & worked solution
  1. A. 48
  2. B. 24
  3. C. 12✓ correct
  4. D. 6

Area =1268sinπ6=2412=12.

Problem #0533 International

Problem 10 Solving Triangles

In ABC, a=7, b=8, c=5. The value of cosC is:

Show answer & worked solution
  1. A. 114
  2. B. 1116
  3. C. 1114✓ correct
  4. D. 58

25=49+64112cosC112cosC=88cosC=88112=1114.

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