Recall that the x% of y can be computed using the following expression:
[tex]y\cdot\frac{x}{100}\text{.}[/tex]Now, since Ravi's chocolate bar is 62% cocoa, and the weight of the chocolate bar is 61 gr, then the chocolate bar contains:
[tex]61\cdot\frac{62}{100}[/tex]grams of cocoa.
Simplifying the above result we get:
[tex]61\cdot0.62=37.82\approx37.8.[/tex]Answer: Ravi's chocolate bar contains 37.8 grams.