The angle does not matter. Think of it as finding the other side to a triangle. Use
a=39 (line AB)
b=b (the leg we need to find)
c=89 (line BD)
(subtract the 1521 from both sides)
(square root both sides)
b = 80
AD=80
<span><span>Let x = the 10's digit
Let y - units digit
then
10x + y = original number
:
Write and equation for each statement:
;
"the units digits of a two-digit number is 3 more than twice the tens digit."
y = 2x + 3
:
"If the digits are reversed, the new number is 9 less than 4 times the original number."
10y + x = 4(10x+y) - 9
10y + x = 40x + 4y - 9
10y - 4y = 40x - x - 9
6y = 39x - 9
:
Find the original number.
:
Substitute (2x+3) for y in the above equation:
6(2x+3) = 39x - 9
12x + 18 = 39x - 9
18 + 9 = 39x - 12x
27 = 27x
x = 1
:
Then using y = 2x+3
y = 2(1) + 3
y = 5
:
Original number = 15
:
:
Check solution in the statement:
"If the digits are reversed, the new number is 9 less than 4 times the original number."
51 = 4(15) - 9</span><span>
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