Question

A length of 1 decameter is represented by 5 cm . Find R.F and construct a plain scale to measure up to 2.5 decameter and Mark a distance 19 metre on it ?​

Answer 1

Answer:

please see the attached image

Answer 2

Answer:

The value of RF is 1/200 cm.

Explanation:

RF scale:

A representative fraction, or RF, depicts the relationship between a unit on the map and a unit on the ground. RFs can be shown as actual fractions, such as 1/24,000, but are more commonly written with a colon, as in 1:24,000.

$rf = \frac{drawing \: lemgth}{actual \: length}$

This is the formula to find RF

BY substituting all the data,

$rf = \frac{5cm}{1 \: decameter}$

1 decameter = 1000 cm

$rf = \frac{5cm}{1 \times 1000 \: cm}$

By simplyfing,

$rf = \frac{1}{200} \: cm$

Hence, RF is found.

The plain scale to measure upto 2.5 decameter,

is given in above image and 19m is marked in the same scale which is useful to understand.

Decameter:

A decametre, symbol dam, is a length unit of ten metres in the International System of Units. While any SI prefix and unit combination can be used, many are rarely used in practise; the decametre is used less frequently than other length units.

Usually 1 decameter is equal to 10 m.

And 19m is marked nearly 1.9 decameter.

Hence, the value of RF is 1/200 cm.

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