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We know that for isosceles triangle ratio of length will be ( \sqrt{2} : 1 : 1)
where \sqrt{2} is the longest side

Also we observe two ants start at A and both end at C!
Thus distance covered by them will be the circumference of their respective semi-circles on which they travel.

For black ant
Distance = pi *(1/2 + 1/2)
Distance for black ant = pi

For red ant
Distance = pi * \sqrt{2}

So, ratio will be \sqrt{2} : 1
Thus, answer is C

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IMO C, in 1:21

As its just about ratios, We can assume values.

Let isosceles triangle sides are 1,1,√2.

As it is ratio common tgis can be ignored.

So distance ratio is red : black

Diameter AC : (AB+BC)
Which is √2:2 = 1:√2,

As we need black to red it is √2:1 option C

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