Questions

Here given that 9 = 63, 8 = 48, 7=35, ... 

The given question follows a pattern that

9 x (9 - 2) = 9 x 7 = 63

8 x (8 - 2) = 8 x 6 = 48

7 x (7 - 2) = 7 x 5 = 35

Similarly, 4 x (4 - 2) = 4 x 2 = 8.

You have to consider three things.

1. First, are the bonds polar?

Look at differences in electronegativity and if  it is >0.5, bonds are polar.

2. Second, does the molecule have unshared electron pairs?

If so, they generally lead to a polar molecule.

3. Third, is the molecule symmetric?

If so, then although the bonds may be polar, the symmetry cancels out the individual bond polarity and the molecule is non polar.

CF4 follows all the rules above and has a symmetric distribution of charge, making it nonpolar. The others all have asymmetric charge distributions.

Hence, CF4 represents a Non-polar molecule.

Let speed of train B be x m/s And length of train B be y m
Then length of train A is 2y m
Speed of train A = 84 × 5/18 = 210/9 m/s = 70/3 m/s
A.T.Q, (2y+y)/10 = 70/3 − x .............(i)
and (2y+y)/ 22.5 = 70/3 − 2x ................(ii)
solving (i) and (ii), y = 50 m

Tetley

• Cactus spines are also known as modified bud scales, which are also called modified leaves.

• Cactus spines occur in clusters in the axil of leaves.

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