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144.F ind the sum of all 2 digituberswdiviside by 2 or 5 |
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Answer» Two digit numbers are : 10,11,12,....,,98,99 numbers divisible by 2 are 10, 12, 14, ...96,98. series APnumbers divisible by 5 are 15, 20,... , 90, 95 there are some common numbers in the two series: 20, 30, 40, ...,90. A.P.Series1 = 10, 12, ..,96, 98 number of terms : (98-10)/2 + 1 = 45 S1 = (first term+last term)/2*number of terms = (10+98)/2*45 = 27*45=1215 sum of numbers divisible by 5 : number of terms = (95 - 15)/5 + 1 = 17 S2 = (95+15) / 2 * 17 = 55 * 17=935 Sum of numbers divisible by 10 : number of terms= (90-20)/10+ 1 = 8 S3 = (90+20)/2 * 8= 55 * 8=440 Answer = S1 + S2 - S3 =1215+935-440 =1710 hit like if you find it useful hit like if you find it useful |
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