Karthik read a book in 25 days. She read 17 pages every day for the first 16 days, and 18 pages everyday for the last 9 days. Which expression do you use to find how many pages Karthik read?

Question

$\begin{array}{11} (a)\; 9 + 18 \\ (b)\; 17 \times 16 + 9 \times 18 \\ (c)\; 25 \times 16 \\ (d)\; 18 \times 9 \end{array}$