Question

A book costs $\$$65. Therefore, 47 such books cost .

• A. $\$$3,055
• B. $\$$2,560
• C. $\$$4,385

Answer 1

The correct option is A $\$$3,055

Cost of 1 book = $\$$65
There are a total of 47 books.

$\text{∴ Cost of 47 books =}\$65\times 47$

Let us solve this using lattice algorithm method.

So, we first make a table containing 2 rows and 2 columns as both 65 and 47 are 2-digit numbers.

After making the table, we extend the diagonals and write 6 and 5 at the top of each column and 4 and 7 against each row.


Now, we multiply the digits in the corresponding rows and columns and write them on each side of the diagonal line.


At last, we add all the digits diagonally. If the summation becomes more than 1 digit, we regroup other digits with the next diagonal to the left.


For the final answer, we write the digits from left to right, that is, 3,055.

$\text{Hence, 47 books cost}\$3,055$