10th Class Mental Ability Mathematical Operations Mathematical Operations

This chapter contains only mathematical operations but in different manner. The main key of solving problem in this chapter is BODMAS rule to which you are already familiar

This chapter consists of the following two types of problems.

1.            Direct Substitution

To solve such type of problems, substitute the symbols \[+,-,\text{ }\times ,\div \] etc., for the given letters or symbol as per the question and simplify the statement using BODMAS rule,

2.            Interchange of Numbers and Signs

To solve such type of problems, interchange the numbers with signs as per the given questions and then apply the BODMAS rule.

EXAMPLE

1.         If '+' stands for \['\times ','{{\times }^{,}}\]stands for \['\div '\]stands for- 'and \['\div '\]stands for ?+? then what is the value of \[8+2\times 4-2\div 6?\]

              (a) 20                                        (b) 12             

              (c) 14                                        (d) 18

Explanation (a):

Given: \[8+2\times 4-2\div 6\]

After replacements above given expression becomes

\[8\times 2-4\div 2+6=8\times 2-2+6=16-2+6=20,\]

2.         Select the correct set of interchanges which would make the given equation true.

 \[\mathbf{8\times 9-3\div 7=13}\]

(a) \[\times \text{ }and\text{ }\div \], 3 and 7                   

(b) \[\times \text{ }and\text{ }\div \], 3 and 8

(c) \[\div and-\], 7 and 8                                                

(d) \[\div and-\]. 3 and 8

Explanation (c):

The given equation is \[8\times 9-3\div 7=13\]

Using interchanges as given in option (c), we get

\[7\times 9\div 3-8=13\]

\[\Rightarrow 7\times 3-8=13\Rightarrow 21-8=13\Rightarrow 13=13,\]which is true.