The arithmetic mean of nineteen numbers is 10. When a twentieth number, x, is added the overall mean becomes 11 . What is the value of x? ( )答案:30Raven Co is considering a new i
1.Over a period, a firm made purchases of $800, $1,000, $1,100 and $1,200 on items, the unit cost of which were $5.00, $6.25, $5.50 and $6.00 respectively.To the nearest cent, the mean price paid per item was ( )A:$5.71B:$5.72C:$5.70D:$5.69