291.If n is an integer between 10 and 99 and n is divisible by 7, the remainder is 3, is n< 80? 1) When n is divided by 5, the remainder is 0 2) When n is divisible by 3, the reminder is 0 Inclusive ?
n = 7m + 3
from 1) à n = 5k à n = 35t + 10, t = 0, 1, 2, 3, … sonot A
from 2) à n = 3s à n = 21a + 24a = 0, 1, 2, 3, …sonot B union à n = 35t + 10 , n = 3s à n = 105 k + 45 在 10 到 99 只有45满足条件 so C 看不明白n=35t+10和n=21a+24这两个算式怎么推出来的????
291.If n is an integer between 10 and 99 and n is divisible by 7, the remainder is 3, is n< 80? 1) When n is divided by 5, the remainder is 0 2) When n is divisible by 3, the reminder is 0 Inclusive ?
n = 7m + 3
from 1) à n = 5k à n = 35t + 10, t = 0, 1, 2, 3, … sonot A
from 2) à n = 3s à n = 21a + 24a = 0, 1, 2, 3, …sonot B union à n = 35t + 10 , n = 3s à n = 105 k + 45 在 10 到 99 只有45满足条件 so C 看不明白n=35t+10和n=21a+24这两个算式怎么推出来的???? 作者: rea89 时间: 2011-3-18 23:59
251与289与你同想法。作者: sasha_wen 时间: 2011-3-19 12:48
顶一下,牛牛帮帮忙作者: zelda爱star 时间: 2011-3-19 17:09
顶一下~ 同问280