Primitive formula

= 156×( 10 1- 1)

= 156× 100

= 15600

Extended data

Simple calculation method:

1, benchmark method

When several numbers close to a certain number are added, you can take a certain number as the reference number, then multiply the reference number with the added number, and add the difference between each number and the reference number to get the calculation result.

For example: 8 1+85+82+78+79.

=80x5+( 1+5+2-2- 1)

=400+5

=405

2. Split method

Mainly, some disassembled scores cancel each other out to simplify the operation. Fractions with the general shape of 1/ax(a+ 1) can be divided into. 1/a- 1/a+ 1 .

For example:11x 2+1/2x3+1/3x4+1/4x5+1/5x6.

= 1_ 1/2+ 1/2- 1/3+ 1/3- 1/4+ 1/4- 1/5+ 1/5- 1/6

= 1- 1/6 (addition and subtraction cancel each other, so the phone can't type it out)

=5/6