Example 7 - Chapter 6 Class 10 Triangles

Last updated at April 16, 2024 by

Example 7 - A girl of height 90 cm is walking away from - Examples

Example 7 - Chapter 6 Class 10 Triangles - Part 2
Example 7 - Chapter 6 Class 10 Triangles - Part 3

Transcript

Example 7 A girl of height 90 cm is walking away from the base of a lamp-post at a speed of 1.2 m/s. If the lamp is 3.6 m above the ground, find the length of her shadow after 4 seconds. Given: Lamp post (AB) = 3.6m Height of girl (CD)=90 cm = 90/100 m = 0.9 m Speed = 1.2 m/sec. To Find : Length of her shadow i.e. DE Solution: - The girl walks BD distance in 4 seconds We know that, Speed = /( ) Speed = /( ) 1.2 = /4 1.2 4= 4.8 = BD = 4.8 m Now , in E = E B = D Therefore, using AA Similarity criterion So, ~ We know that if two triangles are similar, their sides are in proportion / = / ( + )/ = / (4.8 + )/ =3.6/0.9 (4.8 + )/ =36/9 10/10 (4.8 + )/ =4 4.8 + DE = 4 DE 4.8 = 4DE DE 4.8 = 3DE 3DE = 4.8 DE = 4.8/3 DE = 48/(3 10) DE = 16/10 = 1.6 m Hence , shadow is 1.6 m long

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.