CAT Quantitative Aptitude Questions | CAT Algebra - Functions questions

The question is about Greatest Integer Function. Multiplication of a decimal and its Greatest Integer function is given and we need to find out the value of the decimal. Functions is a simple topic which involves a lot of basic ideas. Make sure that you a get of hold of them by solving these questions. A range of CAT questions can be asked based on this simple concept of Functions questions in the CAT Exam. Make sure you practice a lot of questions in CAT Functions Algebra to push your CAT preparation in the right direction. Functions as an idea is a fabulous idea if one can wrap their head around it the right way, and it has been one of the staple ideas tested by the CAT exam historically.

Question 16: Find the value of x for which x[x] = 39?

1. 6.244
2. 6.2
3. 6.3
4. 6.5

Explanatory Answer

Method of solving this CAT Question from CAT Algebra - Functions: Multiplication of a decimal and its and greatest integer function!

When x = 7,
x[x] = 7 * 7 = 49

When x = 6,
x[x] = 6 * 6 = 36

Therefore, x must lie in between 6 and 7 => [x] = 6
=> x = \\frac{45}{[x]}\\) = \\frac{39}{6}\\) = 6.5

The question is "Find the value of x for which x[x] = 39?"

Hence the answer is "6.5"

Choice D is the correct answer.