Question 867349
Let {{{ h[n] }}} be the maximum height of the 
ball after the {{{ n }}}th bounce
{{{ h[n] = 50*.8^n }}}
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{{{ h[1] = 50*.8 }}}
{{{ h[1] = 40 }}}
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{{{ h[2] = 50*.8^2 }}}
{{{ h[2] = 32 }}}
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{{{ h[3] = 50*.8^3 }}}
{{{ h[3] = 25.6 }}}
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Each result is {{{ .8 }}} of the previous result
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{{{ h[10] = 50*.8^10 }}}
{{{ h[10] = 50*.1074 }}}
{{{ h[10] = 5.4 }}} m
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You could do successive multiplications
but I used a calculator