-4
Chat with our AI personalities
First of all, it is the one that is probably not even worth doing. It is honestly easier in most cases to just try it! To determine if a number is divisible by 7, take the last digit off the number, double it and subtract the doubled number from the remaining number. If the result is evenly divisible by 7 (e.g. 14, 7, 0, -7, etc.), then the number is divisible by seven. This may need to be repeated several times.
'121'. 121/3 = 40.3333..... Not divisible. 121/5 any number that does not end in '5' or '0' is not divisible by '5' 121/7 = 17 3/7 Not divisible. 121/9 any number whose digits do not sum to nine is not divisible by '9' ; 1+2+1 = 4
630 is divisible by...2 or 3 or 5 or 6 or 7 or 9. your welcome
The smallest 3-digit multiple of 7 is 105 = 15*7 The largest 3-digit multiple of 7 is 994 = 142*7 So there are 142-14 = 128 3-digit multiples of 7, ie 128 3-digit numbers that are divisible by 7.
Check the Fibonacchi number sequences for 2, 3, 5, & 8 (7 is not a Fibonacchi number).