Simplifying single line addition and subtraction

Sandeep Tripathi

When we face a problem like the one below, this is usually how we follow it in 3 steps :

EXAMPLE 1

2394,465-77.57-2.013 878.95 = ?

By the classical way

Step1: 2394.465 Step 2: -77.570 878.950 – 2.013

3273.415 -79.583

AND,

STEP 3: 3273.415 – 79.583

Answer 3193.832

By the modern way, we can now solve the problem in a single step , as shown below

TECHNIQUE

1. Start with any of the 4 numbers with equal ease.

2. Just put the correct sign of the given number( or – ).

3. Now the last 2 digits ( units place and 10s place) are being solved for you :

5-0-3-0= 2 and 6-7-1 5 =3 ………….. & so on !

We get : 3193.832 Answer .

Caution

1. Don’t forget to put a zero at required place, like 878.95=878.950

2. In case you get a negative digit at any place, you’re free to borrow 1 from any of the positive next digit.

Here’s how : 4217.86-33.68

Here, at the digits place we have 6-8 =-2, so we need to borrow 1 from next place ie. tens place. Borrowing 1 from 8 leaves 7 there , as you usually do and our units place shall be 10 -2 = 8.

This technique can now be extended to larger numbers also.

Try a few more on your own. Happy solving !

The writer is Lecturer (Physics), Govt. Sr. Sec. School, Sector-7, Panchkula