NCERT Class 7 Solutions: Integers (Chapter 1) Exercise 1.1 – Part 3

Q-8 Verify a(b)=a+b for the following values of a and b:

  1. a=21,b=18

  2. a=118,b=125

  3. a=75,b=84

  4. a=28,b=11

Solution:

Given the order of operations in numeric expressions from related equation

Given the Order of Operations in Numeric Expressions

Given the order of operations in numeric expressions from related equation

  1. Given a=21,b=18

    We have a(b)=a+b

    L.H.S=a(b)=21(18)=21+18=39

    R.H.S=a+b=21+18=39

    Since L.H.S=R.H.S

  2. Given a=118,b=125

    We have a(b)=a+b

    L.H.S=a(b)=118(125)=118+125=243

    R.H.S=a+b=118+125=243

    Since L.H.S=R.H.S

  3. Given a=75,b=84

    We have a(b)=a+b

    L.H.S=a(b)=75(84)=74+84=159

    R.H.S=a+b=75+84=159

    Since L.H.S=R.H.S

  4. Given a=28,b=11

    We have a(b)=a+b

    L.H.S=a(b)=28(11)=28+11=39

    R.H.S=a+b=28+11=39

    Since L.H.S=R.H.S

Q-9 Use the sign of >,<or= in the box to make the statement true:

  1. (8)+(4)?(8)(4)

  2. (3)+7(19)?158+(9)

  3. 2341+11?234111

  4. 39+(24)+(15)?36+(52)(36)

  5. (231)+79+51?(399)+159+81

    Smaller numbers whether positive or negative are towards the left.

    Comparing Negative Numbers

    Smaller numbers whether positive or negative are towards the left.

Solution:

  1. (8)+(4)?(8)(4)

    =84?8+4

    =12?4

    =12<4 (-12 is to the left of -4 on the number line and hence is smaller)

  2. (3)+7(19)?158+(9)

    =3+719?1589

    =419?1517

    =15?2

    =15<2 (-15 is to the left of -2 on the number line and hence is smaller)

  3. 2341+11?234111

    =18+11?2352

    =7?29

    =7>29 (-7 is to the right of -29 on the number line and hence is bigger)

  4. 39+(24)+(15)?36+(52)(36)

    =3924+15?3652+36

    =3939?7252

    =0?20

    =0<20 (0 is to the left of 20 on the number line and hence is smaller)

  5. (231)+79+51?(399)+159+81

    =231+79+51?399+159+81

    =231+130?399+240

    =101?159

    =101>159 (-101 is to the right of -159 on the number line and hence is larger)

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