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Question
CBSEENMA10008554

Draw a line segment of length 7.6 cm and divide it in the ratio 5 : 8. Measure the two parts.

Solution

Steps of Construction :
(i)     Draw AB = 5.6 cm
(ii)    At a draw an acute ∠BAX below base AB.
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(iii)    On AX make 5 + 8 i.e. 13 equal parts and mark them as A1, A2, A3, A4,... A13

(iv)    Join B to A13. From A5 draw A5C || A13B. C is the required point of division and AC : CB = 5 : 8.

On measuring, we get
AC = 3.1 cm,
CB = 4.5 cm
Justification :

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[Using basic proportionally theorem]
But space space space space space fraction numerator AA subscript 5 over denominator straight A subscript 5 straight A subscript 13 end fraction space equals space 5 over 8 space
Therefore,    AC over CB space equals space 5 over 8 space

This shows that C divides AB in the ratio 5 : 8.