Question

plzz solve the above question... last one

Answer 1

the longer diameter is 15 or 16 or 18..
that is not clear enough

Answer 2

hEY,

Hope this answer helps!!

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As per given data the above figure is drawn.

O is the common center of two concentric circles

AB→diameter of the bigger circle

AO=OB→radius of the bigger circle=16cm

DO→radius of the smaller circle=10cm

BD→tangent to the smaller circle→∠BDO=90∘

Let ∠DOB=θ⇒∠AOD=(180−θ)

In ΔBDO→cos∠BOD=cosθ=ODOB=1016

Applying cosine law in ΔADO we get

AD2=AO2+DO2−2AO⋅DOcos∠AOD

⇒AD2=AO2+DO2−2AO⋅DOcos(180−θ)

⇒AD2=AO2+DO2+2AO⋅DOcosθ

⇒AD2=AO2+DO2+2AO⋅DO×ODOB

⇒AD2=162+102+2×16×10×1016

⇒AD2=556

⇒AD=√556=23.58cm

__________Hope it helps!