Question

15 members of the Drama Club can make set decorations for their musical in 12 hours. After 4 hours have passed, a few teachers came to help, and the group completed the remaining work in 6 hours. How many teachers helped?

Answer 1

answer = 5 teachers

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Answer 2

Let AB and CD be two lines Intersecting at O, such that, ∠AOD=90 ∘

Now, ∠AOD=∠COB=90 ∘

(Vertically opposite angles)

⟹∠AOD+∠DOB=180 o

(Angles on a straight line)

⟹90+∠DOB=180 o

∠DOB=90 ∘

∠DOB=∠AOC=90 ∘

(Vertically opposite angles)

Thus, all angles are 90 ∘

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