a uniform metre rule of mass 100g balances at the 40cm mark when a mass X is placed at the 10cm mark what is the value of x. pls help I don't know how to solve it

a, c, d, e are all applying about success strategies.

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it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me