Slide25.JPG

Slide26.jpg
Slide27.JPG
Slide28.JPG
Slide29.JPG Slide30.JPG

Go Ad-free

Transcript

Ex 11.1, 9 A 5 m 60 cm high vertical pole casts a shadow 3 m 20 cm long. Find at the same time (i) the length of the shadow cast by another pole 10 m 50 cm high Let’s first convert all lengths in cm 5 m 60 cm = 5 m + 60 cm = 5 × 100 cm + 60 cm = 500 + 60 = 560 cm 3 m 20 cm = 3 m + 20 cm = 3 × 100 cm + 20 cm = 300 + 20 = 320 cm 10 m 50 cm = 10 m + 50 cm = 10 × 100 cm + 50 cm = 1000 + 50 = 1050 cm Ex 11.1, 9 A 5 m 60 cm high vertical pole casts a shadow 3 m 20 cm long. Find at the same time (i) the length of the shadow cast by another pole 10 m 50 cm high Let’s first convert all lengths in cm 5 m 60 cm = 5 m + 60 cm = 5 × 100 cm + 60 cm = 500 + 60 = 560 cm 3 m 20 cm = 3 m + 20 cm = 3 × 100 cm + 20 cm = 300 + 20 = 320 cm 10 m 50 cm = 10 m + 50 cm So, our question becomes A 560 cm high vertical pole casts a shadow 320 cm long We need to find length of shadow cast by pole of height 1050 cm Let y cm be the length of shadow cast by pole of height 1050 cm Thus, our table looks like Now, as height of pole increases, Length of shadow also increases ∴ They are in direct proportion 𝟓𝟔𝟎/𝟑𝟐𝟎 = 𝟏𝟎𝟓𝟎/𝒚 56/32 = 1050/𝑦 56 × 𝑦 = 1050 × 32 𝒚 = (𝟏𝟎𝟓𝟎 × 𝟑𝟐)/𝟓𝟔 𝑦 = (1050 × 16)/28 𝑦 = (1050 × 4)/7 𝑦 = 150 × 4 𝒚 = 𝟔𝟎𝟎 cm 𝑦 = 6 m ∴ Length of shadow is 6 m Ex 11.1, 9 A 5 m 60 cm high vertical pole casts a shadow 3 m 20 cm long. Find at the same time (ii) the height of a pole which casts a shadow 5m long.Now, We need to find height of pole casting a shadow of 5 m i.e. 500 cm Let x be the height of pole which casts a shadow of 500 cm Thus, our table looks like Now, height of pole and Length of shadow are in direct proportion 𝟓𝟔𝟎/𝟑𝟐𝟎 = 𝒙/𝟓𝟎𝟎 56/32 = 𝑥/500 56 × 500 = 𝑥 × 32 28000 = 32x 28000/32 = 𝑥 𝑥 = 28000/32 𝒙 = 875 cm 𝑥 = 8 m 75 cm ∴ Height of the pole is 8 m 75 cm

Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

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 and Computer Science at Teachoo