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The average of four numbers is 638.4. The first 3 are 210, 159.8, and 301.25. Find the fourth.

User Stepheaw
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5 votes
may be he is right but i am not sure 
User Dorjay
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(210 + 159.80 + 301.25 + x) / 4 = 638.40
(671.05 + x ) / 4 = 638.40 ...multiply both sides by 4
671.05 + x = 638.40 * 4
671.05 + x = 2553.6
x = 2553.6 - 671.05
x = 1882.55 <=== the 4th number
User Hestellezg
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