Q5 of 42 Page 156

Write 1 to 10 using 3 and 5, each at least once, and using addition and subtraction. (For example, 7 = 5 + 5 – 3.)

We need to write numbers 1 to 10, using 3 and 5 only, irrespective of how many times we use 3 and 5, using addition and subtraction.

Take number 1,


We know (3 + 3) = 6, and (6 – 5) = 1


1 = 3 + 3 – 5


Take number 2,


Simply subtract 5 and 3.


2 = 5 – 3


Take number 3,


We know, (8 – 5) = 3.


And 8 can be written as (5 + 3), then subtract 5 from the addition.


We get, 3 = (5 + 3) – 5


3 = 8 – 5


Take number 4,


We know, (9 – 5) = 4.


And 9 can be written as (3 + 3 + 3), then subtract 5 from the addition.


We get, (3 + 3 + 3) – 5 = 9 – 5 = 4


4 = 3 + 3 + 3 – 5


Take number 5,


Just cancel 3 from 3, then add 5 to it.


5 = (3 – 3) + 5


Take number 6,


We know, (3 + 3) = 6 but we need to include 5 also. So, just add (5 – 5) to it, it would not mean anything and won’t disturb the equation, while satisfy the question.


6 = 3 + 3 + 5 – 5


Take number 7,


We know, (10 – 3) = 7.


And 10 can be written as (5 + 5), then subtract 3 from it.


We get, (5 + 5) – 3 = 10 – 3 = 7


7 = 5 + 5 – 3


Take number 8,


We know, (5 + 3) = 8


8 = 5 + 3


Take number 9,


Although 9 can be represented by several ways using 5 and 3.


One of the easiest way is:


We know, (3 + 3 + 3) = 9, then add (5 – 5) to it.


9 = 3 + 3 + 3 + 5 – 5


Also, we know 9 = 15 – 6


Where 15 = 5 + 5 + 5


And 6 = 3 + 3


So, 9 = (5 + 5 + 5) – (3 + 3)


9 = 5 + 5 + 5 – 3 – 3


Take number 10,


We know, (5 + 5) = 10.


Just add (3 – 3) to it, it won’t affect the equation.


10 = 5 + 5 + 3 – 3


Hence, we have found the answers.


More from this chapter

All 42 →