The average of 8 numbers is 2.1, the average of the first 3 numbers is 2.6, the average of the last 4 numbers is 1.4, what is the fourth number?

2.1 × 8-2.6 × 3-1.4 × 4 = 16.8-7.8-5.6, = 9-5.6, = 3.4, answer: the fourth number is 3.4

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