Exercise 1D
Page-16
Q1 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
Question 1:
Find each of the following products:
(i) 35×-78
(ii) -92×54
(iii) -611×-53
(iv) -23×67
(v) -125×10-3
(vi) 25-9×3-10
(vii) 5-18×-920
(viii) -1315×-2526
(ix) 16-21×145
(x) -76×24
(xi) 724×(-48)
(xii) -135×(-10)
Answer 1:
(i)
35×-78=3×(-7)5×8=-2140
(ii)
-92×54=(-9)×52×4=-458
(iii)
-611×-53=(-6)×(-5)11×3=3033
Simplifying the above rational number, we get:
3033=30÷333÷3=1011
(iv)
-23×67=(-2)×63×7=-1221
Simplifying the above rational number, we get:
-1221=-12÷321÷3=-47
(v)
-125×10-3=(-12)×105×(-3)=-120-15=12015
Simplifying the above rational number, we get:
12015=120÷315÷3=405=8
(vi)
25-9×3-10=25×3(-9)×(-10)=7590
Simplifying the above rational number, we get:
7590=75÷1590÷15=56
(vii)
5-18×-920=5×(-9)-18×20=-45-360=45360
Simplifying the above rational number, we get:
45360=45÷45360÷45=18
(viii)
-1315×-2526=(-13)×(-25)15×26=325390
Simplifying the above rational number, we get:
325390=325÷5390÷5=6578=65÷1378÷13=56
(ix)
16-21×145=16×14(-21)×5=224-105
Simplifying the above rational number, we get:
224-105=224÷7(-105)÷7=32-15=32×-1-15×-1=-3215
(x)
-76×24=(-7)×246=-1686
Simplifying the above rational number, we get:
-1686=(-168)÷26÷2=843=-84÷33÷3=-28
(xi)
724×(-48)=7×(-48)24=-33624
Simplifying the above rational number, we get:
-33624=-336÷2424÷24=-14
(xii)
-135×(-10)=(-13)×(-10)5=1305
Simplifying the above rational number, we get:
1305=130÷55÷5=26
Q2 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 2:
Verify each of the following:
(i) 37×-59=-59×37
(ii) -87×139=139×-87
(iii) -125×7-36=7-36×-125
(iv) -8×-1312=-1312×(-8)
Answer 2:
(i)
37×-59=-59×37
LHS=3×(-5)7×9 =-1563Simplifying, we get:-1563=-15÷363÷3=-521
RHS=-59×37=(-5)×39×7=-1563Simplifying, we get:=-15÷363÷3=-521
LHS = RHS
(ii)
−87×139=139×−87
LHS=−87×139=(−8)×137×9=−10463
RHS=139×−87=13×(−8)9×7=−10463
LHS=RHS
(iii)
-125×7-36=7-36×-125
LHS =-125×7-36=(-12)×75×(-36)=84180Simplifying, we get: =84÷12180÷12=715
RHS=7-36×-125=7×(-12)(-36)×5=84180Simplifying, we get:=84÷12180÷12=715
LHS = RHS
(iv)
-8 ×-1312=-1312×(-8)
LHS =-8 ×-1312=(-8)×(-13)12=10412Simplifying, we get: =104÷412÷4=263
RHS=-1312×(-8)=(-13)×(-8)12=10412Simplifying, we get: =104÷412÷4=263
LHS = RHS
Q3 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 3:
Verify each of the following:
(i) (57×1213)×718=57×(1213×718)
(ii) -1324×(-125×3536)=(-1324×-125)×3536
(iii) (-95×-103)×21-4=-95×(-103×21-4)
Answer 3:
(i)
(57×1213)×718=57×(1213×718)
LHS=(57×1213)×718=5×127×13×718=6091×718=4201638=1039
RHS=57×(1213×718)=57×12×713×18=57×84234=4201638=1039
∴ (57×1213)×718=57×(1213×718)
(ii)
-1324×(-125×3536)=(-1324×-125)×3536
LHS=-1324×(-125×3536)=-1324×(-12)×355×36=-1324×-420180=54604320=9172
RHS=(-1324×-125)×3536=(-13)×(-12)24×5×3536=156120×3536=156×35120×36=54604320=9172
∴ -1324×(-125×3536)=(-1324×-125)×3536
(iii)
(-95×-103)×21-4=-95×(-103×21-4)
LHS=(-95×-103)×21-4=(-9)×(-10)5×3×21-4=9015×21-4=90×2115×(-4)=-189060=-632
RHS=-95×(-103×21-4)=-95×(-10)×213×(-4)=-95×21012=(-9)×2105×12=-189060=-632
∴ (-95×-103)×21-4=-95×(-103×21-4)
Q4 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 4:
Fill in the blanks:
(i) −2317×1835=1835×(……)
(ii) −38×−719=−719×(……)
(iii) (157×−2110)×−56=(……)×(−2110×−56)
(iv) −125×(415×25−16)=(−125×415)×(……)
Answer 4:
(i) −2317×1835=1835×−2317
(ii) −38×−79=−79×-38
(iii) (157×−2110)×−56=157×(−2110×−56)
(iv) −125×(415×25−16)=(−125×415)×25−16
[∵a×(b×c)=(a×b)×c]
Q5 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 5:
Find the multiplicative inverse (i.e., reciprocal) of:
(i) 1325
(ii) -1712
(iii) -724
(iv) 18
(v) −16
(vi) -3-5
(vii) −1
(viii) 02
(ix) 2-5
(x) -18
Answer 5:
(i) Reciprocal of 1325 is 2513(ii) Reciprocal of −1712 is 12−17, that is, −1217.
(iii) Reciprocal of −724 is 24−7, that is, −247.
(iv) Reciprocal of 18 is 118
(v) Reciprocal of -16 is 1−16, that is, −116.
(vi) Reciprocal of −3−5 is −5−3, that is, 53
(vii) Reciprocal of-1 is -1.
(viii) Reciprocal of 02 does not exist as 20=∞
(ix) Reciprocal of 2−5 is −52
(x) Reciprocal of −18 is -8.
Page-17
Q6 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 6:
Find the value of:
(i) (58)-1
(ii) (-49)-1
(iii) (-7)-1
(iv) (1-3)-1
Answer 6:
We know that a-1=1a or a-1×a=1
(i)(58)-1=85 ∵58×(58)-1=1(ii)(-49)-1=9-4=-94∵-49×(-49)-1=1(iii)(-7)-1=1-7=-17∵-7×(-7)-1=1
(iv) (-3)-1(-3)-1=1-3=-13∵ (-3)-1×(-3) = 1
Q7 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 7:
Verify the following:
(i) 37×(56+1213)=(37×56)+(37×1213)
(ii) -154×(37+-125)=(-154×37)+(-154×-125)
(iii) (-83+-1312)×56=(-83×56)+(-1312×56)
(iv) -167×(-89+-76)=(-167×-89)+(-167×-76)
Answer 7:
(i)LHS=37×(56+1213)=37×(65 +7278)=37×13778=137182RHS=(37×56)+(1213×37)=3×57×6+12×313×7=1542+3691=195+216546=411546=137182
∴ 37×(56+1213)=(37×56)+(37×1213)
(ii)LHS=-154×(37+-125)=-154×(15-8435)=-154×-6935=(-15)×(-69)140=1035140=20728RHS=(-154×37)+(-154×-125)=(-15)×34×7+(-15)×(-12)4×5=-4528+18020=-225+1260140=1035140=20728∴ -154×(37+-125)=(-154×37)+(-154×-125)
(iii)
(-83+-1312)×56=(-83×56)+(-1312×56)LHS=(-83+-1312)×56=-32-1312×56=-4512×56=-45×512×6=-22572=-225÷972÷9=-258RHS=(-83×56)+(-1312×56)=-8×53×6+(-13)×512×6=-4018+-6572=-160-6572=-22572=-225÷972÷9=-258∴ (-83+-1312)×56=(-83×56)+(-1312×56)
(iv)
-167×(-89+-76)=(-167×-89)+(-167×-76)LHS=-167×(-89+-76)=-167×(-16-2118)=-167×-3718=592126=29663RHS=(-167×-89)+(-167×-76)=12863+11242=256+336126=592126=29663∴ -167×(-89+-76)=(-167×-89)+(-167×-76)
Q8 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 8:
Name the property of multiplication illustrated by each of the following statements:
(i) -158×-127=-127×-158
(ii) (-23×79)×-95=-23×(79×-95)
(iii) -34×(-56+78)=(-34×-56)+(-34×78)
(iv) -169×1=1×-169=-169
(v) -1115×15-11=15-11×-1115=1
(vi) -75×0=0
Answer 8:
- Commutative property
- Associative property
- Distributive property
- Property of multiplicative identity
- Property of multiplicative inverse
- Multiplicative property of 0
Q9 | Ex-1D | Rational Numbers | Class 8 | RS AGGARWAL | Chapter 1 | myhelper
OPEN IN YOUTUBE
Question 9:
Fill in the blanks:
(i) The product of a rational number and its reciprocal is .......
(ii) Zero has ....... reciprocal.
(iii) The numbers ....... and ....... are their own reciprocals.
(iv) zero is ....... the reciprocal of any number.
(v) The reciprocal of a, where a ≠ 0, is .......
(vi) The reciprocal of 1a, where a ≠ 0, is .......
(vii) The reciprocal of a positive rational rational number is .......
(viii) The reciprocal of a negative rational number is .......
Answer 9:
(i) 1
(ii) no
(iii) 1; -1
(iv) not
(v) 1a
(vi) a
(vii) positive
(viii) negative
No comments:
Post a Comment