from a set of seven math books, nine science books, and five literature books, in how many ways can a student select two from ea
1 answer:
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Answer:
36
Step-by-step explanation:
Here is the correct and complete question: The units digit of a two-digit number is twice the tens digit. If the digits are reversed, the new number is 9 less than twice the original number. What is the original number?
Lets assume the original number be"10y+x". (x is unit digit and y is 10th digit)
∴ if number is reversed then resulting number be "10x+y".
As given: x= 2y
and
Now, solving the equation to get original number.
Distributing 2 to 10y and x, then opening the parenthesis.
⇒
subtracting by (2x+y) on both side.
⇒
subtituting the value of "x", which is equal to 2y.
∴
⇒
subtracting both side by (16y-9)
⇒
cross multiplying
We get,
y=3
∵x= 2y
∴ x= 6
Therefore, the original number will be 36 as x is the unit number and y as tenth number.