Estimated amount that Mr. Jones thought would be spending each week for grocery = $120
Amount actually spent by Mr.Jones in the grocery store = $94
Error in calculation of the amount of spending = (120 - 94) dollars
= $26
Percentage error in calculation = (26/120) * 100
= (13/6) * 10
= 130/6
= 21.666 percent
= 21.67 percent
So there is 21.67% error in the calculation of Mr. Jones. I hope you got the answer you were looking for.