Multiplication by lattice algorithm

UNIT−2

NUMBERS

Multiplication by lattice algorithm ( up to 2 digit number by 2 digit number and 3 digit number by single digit number)

1. Able to do elementary multiplication of 2 digit by 2 digit and 3 digit by single digit numbers using lattice algorithm and the standard (column) algorithm.

Multiplication of 2 digit by a 2 digit number:

Lattice Algorithm:−

EXAMPLE 1

48 × 36

48 × 36 = 1728

Multiply: 96 × 72

EXAMPLE 2

96 × 72 = 6912

Standard Algorithm:

Multiply: 48 × 36

36 = 30 + 6

EXAMPLE 3

In a school there are 24 desks in each class room. If there are 18 class rooms in the school, Find the total number of desks.

Solution:

Number of desks in each class rooms = 24

Number of desks in 18 class rooms = 18 × 24

24 = 20 + 4

Standard Algorithm:

Multiply: 18 × 24

18 × 24

Multiply 3 digit number by 1 digit number: Lattice Algorithm:

EXAMPLE 1

282 × 9

EXAMPLE 2

647 × 6

Standard Algorithm

EXAMPLE 3

Step: 1

Multiply the ones: 2 ones × 9 = 18 ones

= 8 ones + 10 ones

write 8 in the ones place and carry over 1 to the tens place.

Step: 2

Multiply the tens: 8 tens × 9 = 72 tens.

72 tens + 1 tens = 73 tens

= 70 tens + 3 tens

= 7 hundreds + 3 tens

Write 3 in tens place and carry over 7 to the hundred place.

Step: 3

Multiply the hundreds:

2 hundreds × 9 = 18 hundreds.

18 hundreds + 7 hundreds = 25 hundreds.

= 20 hundreds + 5 hundreds

= 2 thousands + 5 hundreds

EXAMPLE 4

A book has 396 pages. How many pages are there in 9 such books? Solution:

No. of pages in a book = 396 pages

Number of pages in 9 books = 396 × 9

= 3564 pages.