Question 501142
The definition of an average is:
( sum of values of all the samples ) / ( the number of samples )
The number of samples is {{{4}}} (Jan,Feb,Mar,Apr)
Call her earning in April {{{x}}}
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{{{ ( 450 + 320 + 665 + x ) / 4 = 500 }}}
{{{ 1435 + x  = 4*500 }}}
{{{ x = 2000 - 1435 }}}
{{{ x = 565 }}}
She must earn $565 in April to average at least $500 per month Jan-Apr