Question

Three neon signs are turned on at the same time. The first one blinks after every 10 seconds, the second one after every 20 seconds and the third one after every 25 seconds. When will they blink together again if they blinked laast at 9 p.m.?​

Answer 1

Answer:

Answer:

(3) Rs 1800

Step-by-step explanation:

According to the information provided in the question it is given as

120 copies of a book cost= Rs 540

We need to find what will 400 copies of this cost?

Here we use a simple equation for solving this question

Let us assume x is the cost of 400 copies

120 copies = 540 Rupees

400 copies = x Rupees

Now by simple cross multiplication we get the value of x which is the cost value of 400 copies

\begin{gathered}120=540\\ 400= x\\ \end{gathered}

120=540

400=x

\begin{gathered}120 x =540\times 400\\ 120 x= 216000\\ x = \frac{216000}{120} \end{gathered}

120x=540×400

120x=216000

x=

120

216000

Cutting the zero on denominator and numerator

\begin{gathered}x =\frac{21600}{12} \\ x = 1800\end{gathered}

x=

12

21600

x=1800

Hence cost of 400 copies is 1800

Hence option (3) Rs 1800 is correct

Answer 2

Answer:

Given,

3 neon signs blink every 10 secs, 20 secs and 25 secs respectively

To find when they blink again, we need to find the Least Common Multiple (LCM) of these numbers

LCM of 10, 20 and 25

= 100 secs

So, after every 100 secs, they blink at the same time

60 secs = 1 min

100 secs = 60 + 40 secs

= 1 min 40 secs

So, after 1 min and 40 secs, they blink at the same time

Abbreviations

hrs/hr = Hours

mins/min = Minutes

secs/sec = Seconds