Question

the greatest length of a scale that can measure exactly 30cm, 90cm, 1m 20cm, and 1m 35cm lengths is,

Answer 1

Answer:

option c is the right answer..

Here we need to exactly measure these lengths.

Also, lm = 100 cm; ... 1m 35cm = 135cm and 1m 20cm = 120cm

Option 1- 5 cm can measure 30cm, 90cm, 1m 20cm and 1m 35 cm

Option 2 - 10 cm cannot measure 1m 35cm i.e. 135cm

Option 3 -15 cm can measure30cm, 90cm, 1m 20cm and 1m 35 cm

Option 4 -30 cm cannot measure 1m 35cm

Since we want greatest length 15 > 5

∴ Answer = 15cm

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Answer 2

Answer:

15 cm

Explanation:

1m 20 cm = 120 cm

1m 35 cm = 135 cm

Greatest length = HCF of 30, 90, 120 and 135

30 = 2 x 3 x 5

90 = 2 x 3 x 3 x 5

120 = 2 x 2 x 2 x 3 x 5

135 = 3 x 3 x 3 x 5

HCF = 3 x 5 = 15

Therefore, 15 cm is the greatest length of a scale that can measure exactly 30cm, 90cm, 1m 20cm, and 1m 35cm lengths.