I need time machine

Algebra Level 4

A clock loses 5 seconds in every 24 minutes. At 10:00PM on Monday, it is 19 minutes fast. When will it be at the right time?

Friday 5:12 PM Thrusday 6:48 AM Friday 5:12 AM Friday 6:48 PM

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2 solutions

Chew-Seong Cheong
Apr 18, 2016

The clock hands-turning rate ω \omega is 5 5 seconds in 24 24 minutes or ω = 24 × 60 5 24 × 60 = 1435 1440 \omega = \dfrac{24\times 60 - 5} {24\times 60} = \dfrac{1435}{1440} . Let the time lapse after Monday 10:00 \text{10:00} PM be t t , then we have:

t = ω t + 19 × 60 = 1435 1440 t + 1140 5 1440 t = 1140 t = 328320 s ÷ 60 s = 5472 min ÷ 60 min = 91 hr 12 min 91 ÷ 24 hr = 3 days 19 hr 12 min \begin{aligned} t & = \omega t + 19 \times 60 \\ & = \frac{1435}{1440}t + 1140 \\ \Rightarrow \frac{5}{1440}t & = 1140 \\ t & = 328320 \text{ s} \quad \quad \small \color{#3D99F6}{\div 60 \text{ s}} \\ & = 5472 \text{ min} \quad \quad \small \color{#3D99F6}{\div 60 \text{ min}} \\ & = \text{91 hr 12 min} \quad \quad \small \color{#3D99F6}{91 \div 24 \text{ hr}} \\ & = \text{3 days 19 hr 12 min} \end{aligned}

0 : 22 : 00 + 3 : 19 : 12 = 3 : 41 : 12 = 4 : 17 : 12 = Friday 5:12 PM \begin{aligned} \Rightarrow 0:22:00 + 3:19:12 & = 3:41:12 \\ & = 4:17:12 \\ & = \boxed{\text{Friday 5:12 PM}} \end{aligned}

Silver Vice
Apr 18, 2016

Thought , I would post a simple solution.

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