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True False[1 Marks ]

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25 questions · timed · auto-graded

Question 11 Mark
xm ÷ ym = (x ÷ y)m, where x and y are non-zero rational numbers and m is a positive integer.
Answer
True.
Solution:
If x and y are rational numbers, then $\frac{\text{x}}{\text{y}^{\text{m}}}=\frac{\text{x}^{\text{m}}}{\text{y}^{\text{m}}}$
or $\text{x}^{\text{m}}\div\text{y}^{\text{m}}=(\text{x}\div\text{y})^{\text{m}}$
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Question 21 Mark
xm × xn = xm + n, where x is a non-zero rational number and m,n are positive integers.
Answer
True.
Solution:
If x is a rational number and m and n are positive integers, then
am × an
= am+n
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Question 31 Mark
xm + xm = x2m, where x is a non-zero rational number and m is a positive integer
Answer
False.
Solution:
am × an = am+n
xm × xm = xm+m = x2m
Also, ak + ak = 2 ak
So, xm + x= 2 xm
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Question 41 Mark
xm × ym = (x × y)2m, where x and y are non-zero rational numbers and m is a positive integer.
Answer
False.
Solution:
If a and b are rational numbers, then
x× ym = (ab)m
xm × ym = (xy)m = (x × y)m
Hence, $\text{x}^{\text{m}}\times\text{y}^{\text{m}}\neq(\text{x}\times\text{y}^{2\text{m}})$
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Question 51 Mark
x0 × x0 = x0 ÷ x0 is true for all non-zero values of x.
Answer
False.
Solution:
A number in standard form is written as a × 10k, where 1 ≤ a ≤ 10 and k is any integer.
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Question 61 Mark
$\frac{-3^{100}}{5}=\frac{-3^{100}}{-5^{100}}$
Answer
True.
Solution:
$\Big(\frac{-3}{5}\Big)=\Big(\frac{-1\times3}{5}\Big)^{100}$ $\big[\because-3=1\times3\big]$
$\frac{(-1)^{100}\times3^{100}}{5^{100}}$ $\big[\because(\text{a}\times\text{b}^{\text{m}})=\text{a}^{\text{m}}\times\text{b}^{\text{m}}\big]$
$\frac{1\times3^{100}}{5^{100}}$ $\big[\because(-1)^{\text{n}}=1,\text{ if }\text{n}\text{ is even}\big]$
$\frac{3^{100}}{5^{100}}$
Now, taking RHS, we have $\frac{-3^{100}}{-5^{100}}=\frac{3^{10}}{5^{100}}$ [$\because$ if both numerator and denominator have negative sign, then it is cacelled out]
$\therefore$ LHS = RHS
Hence, $\frac{-3^{100}}{-5^{100}}=\frac{3^{10}}{5^{100}}$
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Question 71 Mark
$\Big(\frac{7}{3}\Big)^{2}\times\Big(\frac{7}{3}\Big)^{5}=\Big(\frac{7}{3}\Big)^{10}$
Answer
False.
Solution:
Here,$\Big(\frac{7}{3}\Big)^{2}\times\Big(\frac{7}{3}\Big)^{5}=\Big(\frac{7}{3}\Big)^{2+5}$
$=\Big(\frac{7}{3}\Big)^{7}$ $\big[\because\text{a}^{\text{m}}\times\text{a}^{\text{n}}=\text{a}^{\text{m+n}}\big]$
Here, $\Big(\frac{7}{3}\Big)^{2}\times\Big(\frac{7}{3}\Big)^{5}\neq\Big(\frac{7}{3}\Big)^{10}$
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Question 81 Mark
$\Big(\frac{5}{8}\Big)^{9}\div\Big(\frac{5}{8}\Big)^{4}=\Big(\frac{5}{8}\Big)^{4}$
Answer
False.

Solution:

Here,$\Big(\frac{5}{8}\Big)^{9}\div\Big(\frac{5}{8}\Big)^{4}=\Big(\frac{5}{8}\Big)^{9-4}=\Big(\frac{5}{8}\Big)^{5}$

$\big[\because\text{a}^{\text{m}}+\text{a}^{\text{m}}=\text{a}^{\text{m-n}}\big]$

Hence, $\Big(\frac{5}{8}\Big)^{9}\div\Big(\frac{5}{8}\Big)^{4}\neq\Big(\frac{5}{8}\Big)^{4}$

 

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Question 91 Mark
$\Big(\frac{4}{3}\Big)^{5}\times\Big(\frac{5}{7}\Big)^{5}=\Big(\frac{4}{3}+\frac{5}{7}\Big)^{5}$
Answer
False.
Solution:
Here,$\Big(\frac{4}{3}\Big)^{5}\times\Big(\frac{5}{7}\Big)^{5}=\Big(\frac{4}{3}\times\frac{5}{7}\Big)^{5}$$\big[\because\text{a}^{\text{m}}\times\text{b}^{\text{m}}=(\text{ab})^{\text{m}}\big]$
and $\Bigg[\Big(\frac{4}{3}\Big)^{5}+\Big(\frac{5}{7}\Big)^{5}\Bigg]^{5}$ $\Big[=\Big(\frac{\text{a}}{\text{b}}\Big)+\Big(\frac{\text{c}}{\text{d}}\Big)=\frac{\text{a}}{\text{b}}\times\frac{\text{d}}{\text{c}}\Big]$
$=\Big(\frac{4}{3}\times\frac{5}{7}\Big)^{5}$
Hence, $\Big(\frac{4}{3}\times\frac{5}{7}\Big)^{5}\neq\Big(\frac{4}{3}\times\frac{7}{5}\Big)^{5}$
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Question 101 Mark
$\Big(\frac{2}{5}\Big)^{3}\div\Big(\frac{5}{2}\Big)^{3}=1$
Answer
False.
Solution:
Here, $\Big(\frac{2}{5}\Big)^{3}\div\Big(\frac{5}{2}\Big)^{3}$ $\big[\because=\Big(\frac{\text{a}}{\text{b}}\Big)+\Big(\frac{\text{c}}{\text{d}}\Big)=\frac{\text{a}}{\text{b}}\times\frac{\text{d}}{\text{c}}\big]$
$=\Big(\frac{2}{5}\Big)^{3}\times\Big(\frac{2}{5}\Big)^{3}$ $\big[\because\text{a}^{\text{m}}\times\text{a}^{\text{n}}=\text{a}\text{}^{\text{m+n}}\big]$
$\Big(\frac{2}{5}\Big)^{3+3}=\Big(\frac{5}{2}\Big)^{6}$
Here, $\Big(\frac{2}{5}\Big)^{3}\div\Big(\frac{5}{2}\Big)^{3}\neq1$
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Question 111 Mark
One million = 107
Answer
False.
Solution:
One million = 10 lakhs
= 1000000 = 106
Hence, $10^{6}\neq10^{7}$
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Question 131 Mark
In the standard form, a large number can be expressed as a decimal number between 0 and 1, multiplied by a power of 10
Answer
False.
Solution:
A number in standard form is written as a × 10k, where 1 ≤ a ≤ 10 and k is any integer.
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Question 141 Mark
876543 = 8 × 105 + 7 × 104 + 6 × 103 + 5 × 102 + 4 × 101 + 3 × 100
Answer
True.
Solution:
Take RHS = 8 × 105 + 7 × 104 + 6 × 103 + 5 × 102 + 4 × 101 + 3 × 100
= 8 × 100000 + 7 × 10000 + 6 × 1000 + 5 ×100 + 4 × 10 + 3 × 1
[$\therefore$ a0 = 1]
= 800000 + 70000 + 6000 + 500 + 40 + 3
= 876543
= LHS
Hence, RHS = LHS.
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Question 151 Mark
8 × 106 + 2 × 104 + 5 × 102 + 9 × 100 = 8020509
Answer
True.
Solution:
Take LHS
= 8 × 106 + 2 × 104 + 5 × 102 + 9 × 100
= 8 × 1000000 + 2 × 10000 + 5 × 100 + 9 × 1
[$\therefore$ a0 = 1]
= 8000000 + 2000 + 500 + 9
= 8020509
= RHS
Hence, LHS = RHS.
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Question 161 Mark
600060 = 6 × 105 + 6 × 102
Answer
False.
Solution:
Take RHS = 6 × 105 + 6 × 102
= 6 × 100000 + 6 × 100
$=600000+600=600600\neq\text{LHS}$
Hence, $\text{RHS}\neq\text{LHS}$
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Question 171 Mark
50 × 250 × 1250 = (50)6
Answer
True.

Solution:

Here, 50 × 250 × 1250

= 50 × (5 × 5)0 × (5 × 5 × 5)0

[$\therefore$ 25 = 5 × 5 and 125 = 5 × 5 × 5]

= 50 × 50 × 50 × 50 × 5× 50 [$\therefore$ am × bm = ambm]

= (50)6

Hence, 5× 250 × 1250

= (50)6

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Question 181 Mark
49 is greater than 163
Answer
True.
Solution:
$\therefore$ 163 =(42)3
[$\therefore$ 16 = 4 × 4 = 42]
= 46
Now, in 49 and 46, 49 > 46 as powers 9 > 6
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Question 191 Mark
42 is greater than 24
Answer
False.
Solution:
4= 4 × 4 = 16 [$\therefore$ am = a × a × a ×…× a (m times)]
and 24 =2 × 2 × 2 × 2 = 16
So, 42 = 24
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Question 201 Mark
40 + 50 + 60 = (4 + 5 + 6)0
Answer
False.

Solution:

Here, 40 + 50 + 60

= 1 + 1 + 1

= 3 [$\therefore$ a0 = 1]

and (4+ 5+ 6)0

= (15)0

= 1

Hence, 40 + 50 + 60

$\neq(4+5+6)^{0}$

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Question 211 Mark
4 × 105 + 3 × 104 + 2 × 103 + 1 × 100 = 432010
Answer
False.
Solution:
Take LHS
= 4 × 10+ 3 × 104 + 2 × 103 + 1 × 100
= 4 × 100000 + 3 × 10000 + 2 × 1000 + 1 × 1 [$\therefore$ a0 = 1]
= 400000 + 30000 + 2000 + 1
$=432001\neq\text{RHS}$
Hence, $\text{LHS}\neq\text{RHS}$
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Question 231 Mark
34 > 43
Answer
True.
Solution:
$\therefore3^{4}=3\times3\times3\times3=81$
and 43 = 4 x 4 x 4 = 64
81 > 64
Hence, 34 > 43
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Question 251 Mark
(10 + 10)10 = 1010 + 1010
Answer
False.
Soluton:
We know that, (a × b)m
= am × bm
So, (10 × 10)10
= 1010 × 1010
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True False[1 Marks ] - MATHS STD 7 Questions - Vidyadip