The Average marks of 19 student is 56. the average marks of 10 student is 68 and that of last 10 is 53 then find the marks of 10th student?
Formula of Average :
Average = (a + b)y - nx
By Simple Method:
average of 19 student is= 56
average of first 10 student is= 68
average of last 10 student is= 53
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(10 * 68 + 10 * 53) - 19 * 56
10 (68 + 53) - 19 * 56
10 (121) - 1064
1210 - 1064
146
By Fats Trick:
For fast trick we put the values in the formula (a + b)y - nx
(68 + 53) 10 - 19 * 56
(121) 10 - 1064
1210 - 1064
146
so the average of 10th student is 146.
Watch Youtube video of Speed and Time for better understanding.
