10.5% of what number is 420?

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Answer 1 · 2017-05-09T05:15:59

Number is 4000.

Let the number be #x#.

#therefore# #x(105/1000) = 420#
#rArr# #x = (cancel420 * 1000)/cancel105 = (4 * 1000) = 4000#

Answer 2 · 2017-05-09T05:36:06

#10.5%# of 4000 is #420#

We know that #10.5%# of the number we will call #N# is #420#.
We know that #100# of the number is #N#.

So now we can equate the two lines above by following what we have written:

#10.5/100 = 420/N#

Then cross multiply:

#10.5N = 100*420#

#cancel(10.5)N = 100*cancel(420)4#

#N = 4000#

To check this answer we can calculate #10% or 1/10 of 4000 = 400#

which is reasonably close to the #10.5%# being #420# as given above.