Question

The angle formed by the pages of an open book is?
(a) Acute
(b) Obtuse
(c) Right
(d) Straight

Answer 1

Hint: First, we have to understand each and every angle meaning i.e. Acute angle means angle less than 90. Obtuse angle means angle greater than 90. Right angle means angle exact at 90 i.e. perpendicular and straight angle means angle at 180. Further, using some conditions regarding how we use open books in daily life can give our required answer.

Complete step by step solution:
Here, we will first understand each and every angle given in options.
(i) Acute angle: It means an angle formed which is less than 90 degree i.e. denoted as $<90{}^\circ $ . Example is as shown below:

(ii) Obtuse angle: It means an angle formed which is greater than 90 degree i.e. denoted as $>90{}^\circ $ . Example is shown below.

(iii) Right angle: It means an angle formed at exact 90 degree i.e. perpendicular to on line denoted as $=90{}^\circ $ .

(iv) Straight angle: It changes the direction to point the opposite way. It looks like a straight line having an exact 180 degree denoted as $=180{}^\circ $ .

Now, here we are asked to find what angle is made by pages of an open book. Let's first assume that the book is placed on a table with pages open. So, an imagination figure will look like this.

So, the angle will be less than 180 but greater than 90. Therefore, in this case it is an obtuse angle.
Let’s assume another case where we are reading a book. Then by imagination, diagram will be as below:

In this case also, angle will be obtuse angle.
Thus, the angle formed by the pages of an open book is an obtuse angle.
Hence, option (b) is the correct answer.

Note: Students might take a book that is placed on a table which will be completely flat on the surface, so the angle will be $=180{}^\circ $ . This is a misconception.

This can never happen in daily life because we will not be comfortable reading a book if it is straight angle then. If angle is an acute angle, then also it will be very difficult to read a book and stress will be more to eyes.

So, do not make mistakes while solving such problems.