Two lots of onions with equal quantity, one costing ? 10 per kg and the other costing ? 15 per kg, are mixed together and whole lot is sold at ? 15 per kg. What is the profit or loss?

Let original length = x and original breadth = y.

Original area = xy.

New length =	x	.
	2

New breadth = 3y.

New area =	❨	x	x 3y	❩	=	3	xy.
		2				2

∴ Increase % =	❨	1	xy x	1	x 100	❩%	= 50%.
		2		xy

log10 80	= log10 (8 x 10)
	= log10 8 + log10 10
	= log10 (23 ) + 1
	= 3 log10 2 + 1
	= (3 x 0.3010) + 1
	= 1.9030.

Time from 12 p.m. on Monday to 2 p.m. on the following Monday = 7 days 2 hours = 170 hours.

∴ The watch gains	❨	2 + 4	4	❩min.	or	34	min. in 170 hrs.
			5			5

Now,	34	min. are gained in 170 hrs.
	5

∴ 2 min. are gained in	❨	170 x	5	x 2	❩hrs	= 50 hrs.
			34

∴ Watch is correct 2 days 2 hrs. after 12 p.m. on Monday i.e., it will be correct at 2 p.m. on Wednesday.

Perimeter = Distance covered in 8 min. =	❨	12000	x 8	❩m = 1600 m.
		60

Let length = 3x metres and breadth = 2x metres.

Then, 2(3x + 2x) = 1600 or x = 160.

∴ Length = 480 m and Breadth = 320 m.

∴ Area = (480 x 320) m² = 153600 m².

√l² + b² = √41.

Also, lb = 20.

(l + b)² = (l² + b²) + 2lb = 41 + 40 = 81

⟹ (l + b) = 9.

∴ Perimeter = 2(l + b) = 18 cm.

Let 40% of A =	2	B
	3

Then,	40A	=	2B
	100		3

⟹	2A	=	2B
	5		3

⟹	A	=	❨	2	x	5	❩	=	5
	B			3		2			3

∴ A : B = 5 : 3.

The hands of a clock point in opposite directions (in the same straight line) 11 times in every 12 hours. (Because between 5 and 7 they point in opposite directions at 6 o'clcok only).

So, in a day, the hands point in the opposite directions 22 times.

B runs 35 m in 7 sec.

∴ B covers 200 m in	❨	7	x 200	❩	= 40 sec.
		35

B's time over the course = 40 sec.

∴ A's time over the course (40 - 7) sec = 33 sec.

In 12 hours, they are at right angles 22 times.

∴ In 24 hours, they are at right angles 44 times.