How to solve this can anybody explain

I dont quite understand modulo arithmetic it just feels like confusing symbols so pls help.

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Comments (6)

https://youtu.be/9kFN4gw9cQI

you gotta study the clock darling

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yea i will study it this week

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U FROM JAMSHEDPUR??

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Nope

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Setup — measure each hand as a fraction of the full circle from 12.

position
hour handxx
minute hand12x12x

Swap them:

position after swapwhat it must be
hour hand12x12x12x12x
minute handxx12(12x)=144x12(12x)=144x

So we need 144x144x and xx to be the same point on the dial:

144xx=143x=whole number144x - x = 143x = \text{whole number}

Count:

setconditioncount
valid swaps143xZ143x \in \mathbb{Z}x=0143,,142143x=\tfrac{0}{143},\dots,\tfrac{142}{143}143
hands coincide12xx=11xZ12x-x=11x \in \mathbb{Z}x=011,,1011x=\tfrac{0}{11},\dots,\tfrac{10}{11}11

Coincidences sit inside the 143 (since j11=13j143\frac{j}{11}=\frac{13j}{143}), so subtract:

14311=132143-11=\boxed{132}

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Thanks bhaiya understood!!!

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