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### Question

If $4√5 + √80 = 17.89$, then what is the value of $√125 + 6√5$?

**A**

24.60.

**B**

12.25.

**C**

25.

**D**

12.96.

**Soln.**

**Ans: a**

The given expression can be rearranged like this: $4√5 + √{4^{2} × 5}$, which is same as $4√5 + 4√5$ which is same as $8√5 = 17.89$, from which we get $√5 = 2.24$. Next we can see that $√125 + 6√5$ is same as $√{5^{2} × 5} + 6√5$, which is same as $11√5$, which gives $11 × 2.24$ = 24.60.