Question 359700
{{{Sum = NumberOfTerms*(FirstTerm + LastTerm)/2}}}
{{{342 = n *(16+60)/2}}}
{{{342 = n*76/2}}}
{{{342 = 38n}}}
{{{9 = n }}}
Let the difference between each term be x.
If there are 9 terms, we know that 16+8x = 60 (use one less than 9 )
so
{{{60 - 16 = 8x}}}
{{{44 = 8 x}}}
{{{x = 5.5}}}