1.

The length of the common chord of two circles of radii 15 and 20, whose centres are 25 units apart, isA. 24B. 25C. 15D. 20

Answer» Correct Answer - A
Let `C_(1) and C_(2)` be the centres of the two circles of radii r and R respectively. Then,
`C_(1)C_(2)=25, r=15 and R=20 `[Given]
We observe that `C_(1)C_(2)^(2)=r^(2)+R^(2)`
Thus, the two circles, intersect orthogonally .
`:.` Length of the common chord `=(2rR)/(sqrt(r^(2)+R^(2)))=(2xx15xx20)/(25)=24`


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