Page 50 - Start Up Mathematics_8 (Non CCE)

Thinking Skills

1. Simplify:

 − 2 1  − 10  5 − 1  2



− 4     4  − 1   5       2  − 3  15  3   15 
. (
(a) 0 000125 3 ) (b)         (c)      ÷     
     5           5   4   
 
       
   
2. Evaluate:
1 1 1 1
(a)  390625 8  (b)  117649  6 (c) ( 32768 15 ) (d) ( 279936 7 )




 6561   1771561 
−
1
 1  3   − 1


−
–1 2
–1
6
3. Find a number which when divided by {(3) + (2) } gives the quotient as () +    .

   2   
Values and Life Skills
11
The distance between the sun and the earth is 1.496 × (10) m and the distance between the earth and the
8
moon is 3.84 × (10) m. During a solar eclipse, the moon comes in between the earth and the sun. At that
time, what is the distance between the moon and the sun? Is it safe to watch solar eclipse with naked eye?
Some NCERT Textbook Questions
1. Simplify and express the result in power notation with positive exponent.
 1  2  5  4
4
5
(i) (–4) ÷ (–4) 8 (ii)  3  (iii) (–3) ×  
 2   3 
–5
–10
–3
–7
(iv) (3 ÷ 3 ) × 3 (v) 2 × (–7) –3
2. Find the value of
 1  − 2  1  − 2  1  − 2
–1
–1
2
–1
(i) (3° + 4 ) × 2 (ii) (2 × 4 ) ÷ 2 –2 (iii)   +   +  

3 
4 
2 


3. Simplify
5
−
5
−
25×t − 4 3 × 10 × 125
(i) t ( ≠ 0) (ii)
−
7
−
3
5 × 10×t − 8 5 × 6 − 5
4. Express the number appearing in the following statements in standard form.
1
(i) 1 micron is equal to m .
1000000
(ii) Charge of an electron is 0.000, 000, 000, 000, 000, 000, 16 coulomb.
(iii) Size of a bacteria is 0.0000005 m
(iv) Size of a plant cell is 0.00001275 m
(v) Thickness of a thick paper is 0.07 mm
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