Out of possible 250 marks Keith scored 91 percent How many extra marks would he have needed to score 95 percent?

Solution if one acts before thinking:

91% of 250 = 227.5

95% of 250 = 237.5

(237.5) - (227.5) = 10 extra marks required to raise score to 95%.

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Solution if one thinks before acting:

Additional score required = (95% - 91%) = (4% of 250) = 10 marks