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Pythagoras' Theorem 1

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Find the length of the side marked 𝑥. Give your answer correct to 3 significant figures.

Find the length of the side marked 𝑥

Find the sum of the squares of the two given sides:

5cm

10cm

𝑥

𝑥

5cm

10cm

5cm

𝑥

10cm

10cm

𝑥

5cm

cm

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Correct

This is not correct.
𝑥² = 16² + 7²
    = 256 + 49
    = 305
𝑥 = √305
   = 17.5cm  (to 3 s.f.)

𝑥² = 9² + 5²
    = 81 + 25
    = 106
𝑥 = √106
   = 10.3cm  (to 3 s.f.)

𝑥² = 23² + 11²
    = 529 + 121
    = 650
𝑥 = √650
   = 25.5cm  (to 3 s.f.)

𝑥² = 15² + 7²
    = 225 + 49
    = 274
𝑥 = √274
   = 16.6cm  (to 3 s.f.)

𝑥² = 2² + 1²
    = 4 + 1
    = 5
𝑥 = √5
   = 2.24cm  (to 3 s.f.)

This is not correct.
𝑥² = 10² + 6²
    = 100 + 36
    = 136
𝑥 = √136
   = 11.7cm  (to 3 s.f.)


We are finding the longest side so we need

to square the other two sides and add them.

You subtracted rather than added.

This is not correct.
𝑥² = 16² + 8²
    = 256 + 64
    = 320
𝑥 = √320
   = 17.9cm  (to 3 s.f.)


You didn't square the 16.

This is not correct.
𝑥² = 21² + 9²
    = 441 + 81
    = 522
𝑥 = √522
   = 22.8cm  (to 3 s.f.)

You didn't square the 9.

This is not correct.
𝑥² = 2² + 1²
    = 4 + 1
    = 5
𝑥 = √5
   = 2.24cm  (to 3 s.f.)

You didn't square root the 5.

This is not correct.
9² + 4² = 81 + 16
            = 97

This is not correct.
17² + 8² = 289 + 64
              = 353

This is not correct.
21² + 11² = 441 + 121
                = 562

This is not correct.
12² + 6² = 144 + 36
              = 180

We are finding the sum of the squares

so the squares need to be added. You

subtracted rather than added.

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