i wondering how my fren can solve this question within 5 seconds. the question is : 9999*1234=? she can solve it rlly fast without calculation and calculator. she ask me to gv any 4 numbers and she times it with 9999. is tis a math trick? how to count?
2007-05-09 23:31:05 · 5 answers · asked by jaystyle4eva 1 in Science & Mathematics ➔ Mathematics
Not a trick really!
Consider 5678*9999
= 5678(10000-1)
= 56780000 - 5678
= 56774322
but u'have to do fast subtraction...I prefer this method....u'll take 3-4 seconds!
Thumb rule for 9999.....multiply the number with 10000 and subtract from that the number itself.
The smaller the number easier to do!!
2007-05-09 23:35:20 · answer #1 · answered by Som™ 6 · 1⤊ 0⤋
She just multiplies by 10000 = 12340000, then subtracts 1234 from that to give 12338766.
It is a trick because she doesn't need to long multiply two 4 digit numbers, just move the decimal point 4 places and do a simple subtraction.
2007-05-10 06:41:11 · answer #2 · answered by All Black 5 · 0⤊ 0⤋
9999*1234=10000*1234 - 1234
2007-05-10 06:41:46 · answer #3 · answered by Srbo Sutaric 5 · 0⤊ 0⤋
just do this
1234*10000-1234
2007-05-10 06:53:00 · answer #4 · answered by maheer_bd 1 · 0⤊ 0⤋
Maybe just the four digit number times10⁴ ,
less the original four digit number .
2007-05-10 06:49:09 · answer #5 · answered by Zax 3 · 0⤊ 0⤋