Pic of chapter exponents and powers for class 8 or 9❤️❤️❤️❤️
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Class VIII Math
NCERT Solution for Exponents and Powers
EXERCISE: 12.1 (Page 197)
Q1. Evaluate:
(i) 3�2(ii) (�4)�2(iii)
Q2. Simplify and express the result in power notation with positive exponent.
Q3. Find the value of:
Q5. Find the value of m for which 5m ÷ 5–3 = 55.
Sol. ∵ am ÷ an = am – n
∴ L.H.S = 5m ÷ 5–3
= 5m–(–3) = 5m + 3
Now 5m + 3 = 55
Since, bases 5 are equal, therefore exponents are also equal.
i.e. m + 3 = 5
or m = 5 – 3 = 2
Thus, the required value of m is 2.
EXERCISE: 12.2 (Page 200)
Q1. Express the following numbers in standard form.
(i) 0.0000000000085
(ii) 0.00000000000942
(iii) 6020000000000000
(iv) 0.00000000837
(v) 31860000000
Q2. Express the following numbers in usual form.
(i) 3.02 � 10�6(ii) 4.5 � 104(iii) 3 � 10�8 (iv) 1.0001 � 109(v) 5.8 � 1012(vi) 3.61492 � 106
Sol. (i) 3.02 � 10�6 = 302 � 10�2 � 10�6
= 302 � 10�8
Q3. Express the number appearing in the following statements in standard form.
(i) 1 micron is equal to
(ii) Charge of an electron is 0.000,000,000,000,000,000,16 coulomb.
(iii) Size of a plant cell is 0.00001275 m.
(iv) Size of a plant cell is 0.00001275 m.
(v) Thickness of a thick paper is 0.07 mm.
Sol.
Q4. In a stack there are 5 books each of thickness 20 mm and 5 paper sheets each of thickness 0.016mm. What is the total thickness of the stack?
Sol. ∵ Thickness of one book = 20 mm
∴ Thickness of 5 books = 5 × 20 mm = 100 mm
Again,
Thickness of 1 paper sheet = 0.016 mm
∴ Thickness of 5 paper sheets = 5 × 0.016 mm
= 0.080 m
∴ Total thickness = 100 mm + 0.080 mm
= 100.08 mm = 1.0008 × 102 mm