To determine the number of trout in a lake, a conservationist catches 109 trout, tags them and throws them back into the lake. later, 30 trout are caught; 15 of them are tagged. how many trout would the conservationist expect to be in the lake?

The conservationist expects 124 trouts.

SOLUTION:

Given, To determine the number of trout in a lake, a conservationist catches 109 trout, tags them and throws them back into the lake.  

Later, 30 trout are caught; 15 of them are tagged.  

We have to find how many trout would the conservationist expect to be in the lake?

Now, initially, trout count = 109

Then, again 30 trouts caught then, trout count = 109 + 30

But 15 of them are tagged which means they are part of 109 trouts so we should not count again in 30 trouts.

So, trout count = 109 + 30 – 15 = 109 + 15 = 124.

Hence, the conservationist expects 124 trouts.