NCERT Exemplar Solutions
Class 7 - Mathematics - Unit 1: Number System - Multiple Choice Questions
Question 18

Question.  18

\(–35\times 107\) is not same as

(a)

\(–35\times(100+7)\)

(b)

\((–35)\times 7 + (–35)\times 100\)

(c)

\(–35\times 7 + 100\)

(d)

\((–30–5)\times 107\)

Detailed Answer with Explanation:

Why (c) is NOT the same as ((-35) imes 107)

Key idea: Use the distributive property:

(a imes(b+c)=a imes b+a imes c)

Check (a): ((-35) imes(100+7))

First, note that:

(100+7=107)

So,

((-35) imes(100+7)=(-35) imes107)

Also, expanding by distributive law:

((-35) imes(100+7)=(-35) imes100+(-35) imes7)

So (a) matches the original.


Check (b): (((-35) imes 7)+((-35) imes 100))

This is exactly the expanded form from (a), just the two parts are written in swapped order. Addition order doesn’t change the sum:

((-35) imes100+(-35) imes7 = (-35) imes7+(-35) imes100)

So (b) also matches the original.


Check (c): ((-35) imes 7 + 100)

Carefully compare with the correct expansion:

( ext{Correct: }(-35) imes100+(-35) imes7)

But option (c) has:

((-35) imes7+100)

Notice the problem: the 100 is not multiplied by ((-35)). It should be ((-35) imes100), not just (+,100).

To be extra sure, check the actual values:

((-35) imes107=-3745)

((-35) imes7+100=-245+100=-145)

(-3745 eq -145). So (c) is not the same.


Check (d): (( -30 - 5) imes 107)

Here, (-35) is rewritten as (-30-5):

(-35=-30-5)

Apply distributive property:

(( -30 - 5) imes 107=(-30) imes107+(-5) imes107)

Combine:

((-30-5) imes107=(-35) imes107)

So (d) also matches the original.


Conclusion: Only option (c) is not the same as ((-35) imes107).

NCERT Exemplar Solutions Class 7 – Mathematics – Unit 1: Number System – Multiple Choice Questions | Detailed Answers