a number is posed of 4 digits .the last digit is equal to 4 times the first digit,the second digit is equal to 6 times the first digits and the third digit is equal to 3 plus the second digit .what's the sum of this number's digits 英语
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【答案】 由于每位数只能是0-9,从“second digit is equal to 6 times the first digits”可以知道,第1位只能是1,第2位只能是6.所以其他两位是9,4.这个数字是1694
the sum of this number's digits=1+6+9+4=20