Pipes A and B can fill a tank in 5 and 6 h, respectively. Pipe C can fill it in 30 h. If all the three pipes are opened together, then in how much time the tank will be filled up?

Let (17.28 ÷ N ) / (3.6 x 0.2) = 2
Then, 17.28 / N = 1.44
? N = 17.28 / 1.44
= 12

? a + (1/b) = 1
ab + 1 = b ......(i)

Also, b + (1/c) = 1
? b = 1 - (1/c) ....(ii)

From Eqs. (i) and (ii), we get
ab + 1 = 1 - (1/c)
? ab = -1/c
? abc = -1

Draw a figure as per given question,
In a Right triangle ADC, Use the (Pythagoras Theorem)
AC = ?DC² - AD²
? AC = ? 15² - 9 ²
? AC = ? 225 - 81
? AC = ? 144
? AC = 12 cm
In a Right triangle BCE, Use the formula
CB = ? CD² - BE²
? CB = ?15 ² - 12²
? CB = ?225 - 144
? CB = ? 81
? CB = 9 m

? Width of the street (AC + BC) = AB = 12 + 9 = 21 m.

Series pattern 4 x 0.5 = 2
2 x 1.5 = 3
Should come in place of 3.5
3 x 2.5 = 7.5
7.5 x 3.5 = 26.25
26.25 x 4.5 = 118.125
Clearly, 3.5 is wrong and is replaced by 3.

Let the number be p and q.
According to question,
(p + q)² = 4pq
? p² + q² + 2pq ? 4pq = 0
? (p ? q)² = 0
? p = q
Hence , required ratio is 1 : 1 .

According to the question,
4a = 68 [ where a = side]
?a = 68/4 = 17 cm

? Required area = a²
= (17)² = 289 sq cm

Area = 1/2 hectare = 10000 / 2 m²
= 5000 m²

Again Area = 1/2 x (Diagonal)²

So 1/2 x (Diagonal)² = 5000m²
? Diagonal²= 10000
? Diagonal = 100