Question

Dennis thought of a number. He adds 0.5 to that number and then multiplies the new result by 4. He then subtracts 2 and divides the number by 2. His final answer is 48. What number did Dennis start with?

Answer 1

Let the number Dennis thought about be x.
Then adding 0.5 it becomes x+0.5. 
Multiplying by 4, he had 4(x+0.5) =4x+2.
Subtracting 2, the number became 4x+2-2 =4x
Diving the number by 2, he had 4x/2 =2x
But the final number is 48.
∴ 2x = 48
⇒ x = 48/2
⇒ x = 24
Answer: The number that Dennis started with was 24.

Answer 2

Given:

Dennis thought of a number.

Adds 0.5

Multiplies by 4

Subtracts 2 from it

Divides by 2

Result = 48

Solution:

Consider the number to be x.

Dennis adds 0.5. So, (x + 0.5)

Multiplies by 4. So, ( x + 0.5 )4. We get, (4x + 2)

Dennis subtracts 2. So, ( 4x + 2 - 2 ). We get, 4x

Divides by 2. So, 4x/2. We get, (2x)

He got the result as 48.

So, 2x = 48

Then,

x = 48 ÷ 2

x = 24

Hence, The number is 24.

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