@[email protected] to Lemmy [email protected] • 1 year agoPaniki.postimg.ccmessage-square143fedilinkarrow-up11.28K
arrow-up11.23KimagePaniki.postimg.cc@[email protected] to Lemmy [email protected] • 1 year agomessage-square143fedilink
minus-square@[email protected]linkfedilink16•1 year ago7 is double the last number and subtract from the rest 749 (easily divisible by 7 but for example sake) 9*2=18 74-18=56 6*2=12 5-12= -7, or if you recognize 56 is 7*8… I’ll do another, random 6 digit number appear! 59271 1*2=2 5927-2=5925 5*2=10 592-10=582 2*2=4 58-4=54, or not divisible I guess for this to work you should at least know the first 10 times tables…
minus-square@[email protected]linkfedilink17•1 year agoAnother way to tell if 59271 is divisible by 7 is to divide it by 7. It will take about the same amount of time as the trick you’re presenting, and then you’ll already have the result.
minus-square@[email protected]linkfedilink5•1 year agoBut at least I seems like you could do that trick in your head
7 is double the last number and subtract from the rest
749 (easily divisible by 7 but for example sake)
9*2=18
74-18=56
6*2=12
5-12= -7, or if you recognize 56 is 7*8…
I’ll do another, random 6 digit number appear!
59271
1*2=2
5927-2=5925
5*2=10
592-10=582
2*2=4
58-4=54, or not divisible
I guess for this to work you should at least know the first 10 times tables…
Another way to tell if 59271 is divisible by 7 is to divide it by 7. It will take about the same amount of time as the trick you’re presenting, and then you’ll already have the result.
But at least I seems like you could do that trick in your head
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