Question

Solve the given problem:
 $ - 20 \times 123 $

Answer 1

Hint: When we are given an ‘into’ symbol denoted by ‘ $ \times $ ’, between two numbers, it means that we need to perform the operation of multiplication between the elements on either side of the symbol ‘ $ \times $ ’. If while multiplying two terms, any of the terms ends with $ 0 $ , keep it aside till the last step then multiply the final answer with the total number of zeroes present at the end.

Complete step-by-step answer:
In the question we are required to solve this operation: $ - 20 \times 123 $
From the given question we know that the integers present are: $ - 20,123 $
The operation we need to perform is ‘ $ \times $ ’: so we identified the operation to be multiplication of $ - 20,123 $ .
The answer we get when we multiply terms is said to be the ‘product’.
Firstly we need to be thorough with the basic multiplication tables, we should know the tables of integers from $ 1 $ to $ 10 $ .
Once we are familiar with the multiplication tables , keep a few basic points in mind that can help us find the product easily.
Then we have terms with different signs ( $ + $ or $ - $ ), we can proceed to multiply the numbers first then put the signs later. Just remember that $ ( + ) \times ( + )\;\; = \;( + ) $ , $ ( + ) \times ( - )\;\; = \;( - ) $ and $ ( - ) \times ( - )\;\; = \;( + ) $ .
When we have numbers containing zeros in its unit place, keep the zeroes aside and first finish multiplying between the terms without the zero at its unit place. Once we have found the result we can just place the number of zeroes that were present at the end of the original terms considered for multiplication.
* For example, if we needed to find the product of $ 300 $ and $ 20 $ , then we first multiply $ 3 \times 2 $ and write the result $ 6 $ , then again multiply $ 6 $ with $ 1000 $ (because we left out three zeros from the first product calculation). Then the final answer for $ 300 \times 20 = 6000 $ . This not only makes multiplication easier, it also helps us to save time while multiplying numbers with many zeroes at the end.
Now we proceed to the given question, we see here that one of the terms has a zero in its unit place and there is one negative term so we can break down or simplify and write the product as:
 $ - 20 \times 123 = - 1 \times 10 \times 2 \times 123 $
 $ = 2 \times 1230 $
 $ = 2460 $
So, the correct answer is “2460”.

Note: If another symbol ‘ $ + $ ’ was given between the terms $ - 20 $ and $ 123 $ , then we would perform the operation ‘addition’ between the given integers. Addition of these terms where one is positive and the other is negative, is basically subtraction between the terms and the sign given to the final answer will be the sign of the bigger integer among the given integers.
 $ \therefore \; - 21 + 123 = 102 $