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7th Grade > Mathematics

EXPONENTS AND POWERS MCQs

Total Questions : 102 | Page 7 of 11 pages
Question 61.


Find the difference between 45 and 54?  [2 MARKS]


 Discuss Question
Answer: Option A. ->
:

Steps: 1 Mark
Answer: 1 Mark
45=(4)×(4)×(4)×(4)×(4)
45=1024
54=(5)×(5)×(5)×(5)
54=625
The difference between 45 and 54 is
4554=1024625

4554=399
The difference between 45 and 54 is 399.


Question 62.


Is 30=(1000)0 true or false?  Justify your answer. [2 MARKS]


 Discuss Question
Answer: Option A. ->
:
Concept: 1 Mark
Answer: 1 Mark
Consider,    30=(1000)0
L.H.S. is 30=1   [ a0 = 1]
and R.H.S. (1000)0=1    [ a0 = 1]
L.H.S. = R.H.S.
30=(1000)0.
It is true.
We should remember that any non-zero number raised to the power 0 is always equal to 1.
Question 63.


Simplify: 84×143×5×3445×73×62  [3 MARKS]


 Discuss Question
Answer: Option A. ->
:

Application: 1 Mark
Steps: 1 Mark
Answer: 1 Mark
Consider,
84×143×5×3445×73×62
84=(23)4=212
143=(2×7)3=23×73
45=(22)5=210
62=(2×3)2=22×32
On substituting the values we get:
212×23×73×5×34210×73×22×32
=212+3102×733×5×342 [ aman=amn]
=23×5×32   [a0=1]
=8×5×9
=360


Question 64.


When a number is multiplied with 25 it gives 78125. Find the number and express it as a power of 5. What is the product if the number is multiplied by (5)×(5)?  [3 MARKS]


 Discuss Question
Answer: Option A. ->
:

Concept: 1 Mark
Application: 1 Mark
Answer: 1 Mark
Let the number be x.
Given that,

(x)×(25)=78125
x=3125
The required number is 3125
Now,
3125=5×5×5×5×5

3125=55
Now, if the number was multiplied by (5)×(5) then the product=(5)×(5)×3125 = 78125


Question 65.


A shopkeeper A has Rs 34265 in his counter and shopkeeper B has 432500 paise in his counter. Express the difference in rupees in standard form. [ 3 MARKS]


 Discuss Question
Answer: Option A. ->
:

Conversion: 1 Mark
Difference: 1 Mark
Standard form: 1 Mark
As per the question
The amount shopkeeper A has = Rs 34265.
The amount shop keeper B has = 432500 paise  Rs 4325.
Difference = Rs 34265 - Rs 4325 = Rs 29940.
The standard form of Rs 29940.
29940=2.994×104
The difference in rupees is 2.994×104


Question 66.


A ball is released from a height of x meters. Given that it bounces back to half of its original height. Find the product of heights after eight bounces.  [4 MARKS]


 Discuss Question
Answer: Option A. ->
:

Formula: 1 Mark
Application: 1 Mark
Answer: 2 Marks
Given that
The ball is released from a height of x m
Height reached after first bounce =x2
Height reached after second bounce =x4=x22
Height reached after third bounce =x8=x23
Height reached after fourth bounce =x16=x24
Height reached after fifth bounce =x32=x25
Height reached after sixth bounce =x64=x26
Height reached after seventh bounce =x128=x27
Height reached after eight bounce =x256=x28
Product of first 9 heights =x×x2×x22×x23×x24×x25×x26×x27×x28
=x(1+1+1+1+1+1+1+1+1)2(1+2+3+4+5+6+7+8)
(ab×ac = ab+c)
=x9236
The product of heights after 8 bounces =x9236


Question 67.


Express each of the following numbers using the exponential notation:
(i) 512
(ii) 343
(iii) 729


 Discuss Question
Answer: Option A. ->
:
Each option: 1 Mark
i)512=2×2×2×2×2×2×2×2×2=29
ii)343=7×7×7=73
iii)729=3×3×3×3×3×3=36
Question 68.


A man X has a land whose area is 34 meter square and a man Y has 43 meter square of land. If the land costs Rs 50 per meter square, who has higher property value? [4 MARKS]


 Discuss Question
Answer: Option A. ->
:

Step: 2 Marks
Application: 1 Mark
Answer: 1 Mark
The area of land owned by X is
=34 m2=81 m2

The value of given property is
=(81)×(50)=Rs.4050

The area of land owned by Y is 
43 m2=64 m2
The value of given property is
=(64)×(50)=Rs.3200

Value of property owned by X is greater than property owned by Y.
 


Question 69.


Simplify:  [4 MARKS]
i)(58)7×(85)5
ii)(25)2×7383×7


 Discuss Question
Answer: Option A. ->
:
Each: [2 Marks]
i)(58)7×(85)5
=5787×8555
=5755×8587
=5(7)(5)×8(5)(7)
( aman=amn)
=52×82=8252=6425
ii)(25)2×7383×7
(25)2×7383×7
= (25×2)×73(23)3×7
((am)n=am×n)
= 210×7329×7
=2109×731=2×72
=2×49=98
Question 70.


If abc = 1, then find the value of:
11+a+b1+11+b+c1+11+c+a1  [4 MARKS]


 Discuss Question
Answer: Option A. ->
:
Formula: 1 Mark
Steps: 2 Marks
Answer: 1 Mark
Given that,
abc=1
So, c=1÷ab=(ab)1
Similarly,
 a=(bc)1
b=(ac)1
And,
ab=c1
ac=b1
bc=a1
11+a+b1+11+b+c1+11+c+a1
=11+a+b1+b1b1+bb1+b1c1+aa+ac+aa1  
[Multiplying 2nd term by b1b1 and 3rd term by aa]
=11+a+b1+b1b1+1+a+aa+b1+1
 aman=amn
=1+b1+a1+a+b1
=1

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