Answer 1

\[\text{ Here, x and y vary directly }  . \]
\[ \therefore x = ky\]

\[ x = 6 \text{ and }  y = 15\]
\[i . e . , 6 = k \times 15\]
\[ \Rightarrow k = \frac{6}{15} = 0 . 4\]
\[\text{ For x = 10 and k = 0 . 4, we have: }  \]
\[y = \frac{10}{0 . 4} = 25\]
\[\text{ For y = 40 and k = 0 . 4, we have: } \]
\[x = 0 . 4 \times 40 = 16\]
\[\text{ For x = 20 and k = 0 . 4, we have: } \]
\[y = \frac{20}{0 . 4} = 50\]