Prove that the difference between a two-digit number and the product of its digits will always be a 2 digit number.

Mathematics

2 answers:

slamgirl [31]2 years ago

7 0

Step-by-step explanation:

Let the two-digit number is $xy$

This can be written as:

10x + y, where 1 ≤ x ≤ 9 and 0 ≤ y ≤ 9

The difference between the number and product of its digits is:

d = 10x + y - xy

Rewrite this as below:

d = 10x - xy + y - 10 + 10 =

x(10 - y) - (10 - y) + 10 =

(x - 1)(10 - y) + 10

We see that:

0 ≤ x - 1 ≤ 8 according to the condition given above
1 ≤ 10 - y ≤ 10 again according to the condition given above

The value of d is then:

0 + 10 ≤ d ≤ 8*10 + 10
10 ≤ d ≤ 90

<h3>Proved</h3>

Andre45 [30]2 years ago

5 0

Solution:

Let's take the greatest two-digit number as an example.

=> 99

Proving...

99 - (9 x 9) = Two-digit number
=> 99 - 81 = Two-digit number
=> 18 = Two-digit number

Since the difference between the greatest two-digit number and the product of its digits is a two-digit number, the difference between the other two-digit numbers '10, 11, 12.... 97, 98' and the product of its digits will always be a two-digit number, as the product of its digit is less than the two-digit number.

Hence proved. ✔✔

You might be interested in

Please help. How do you find cosine, sine, cosecant and secant with this triangle?

Veseljchak [2.6K]

Hi there! You have to remember these 6 basic Trigonometric Ratios which are:

sine (sin) = opposite/hypotenuse
cosine (cos) = adjacent/hypotenuse
tangent (tan) = opposite/adjacent
cosecant (cosec/csc) = hypotenuse/opposite
secant (sec) = hypotenuse/adjacent
cotangent (cot) = adjacent/opposite
cosecant is the reciprocal of sine
secant is the reciprocal of cosine
cotangent is the reciprocal of tangent

Back to the question. Assuming that the question asks you to find the cosine, sine, cosecant and secant of angle theta.

What we have now are:

Trigonometric Ratio
Adjacent = 12
Opposite = 10

Looks like we are missing the hypotenuse. Do you remember the Pythagorean Theorem? Recall it!

a²+b² = c²

Define that c-term is the hypotenuse. a-term and b-term can be defined as adjacent or opposite

Since we know the value of adjacent and opposite, we can use the formula to find the hypotenuse.

10²+12² = c²
100+144 = c²
244 = c²

Thus, the hypotenuse is:

$\large \boxed{c = 2 \sqrt{61} }$

Now that we know all lengths of the triangle, we can find the ratio. Recall Trigonometric Ratio above! Therefore, the answers are:

cosine (cosθ) = adjacent/hypotenuse = 12/(2√61) = 6/√61 = (6√61) / 61
sine (sinθ) = opposite/hypotenuse = 10/(2√61) = 5/√61 = (5√61) / 61
cosecant (cscθ) is reciprocal of sine (sinθ). Hence, cscθ = (2√61/10) = √61/5
secant (secθ) is reciprocal of cosine (cosθ). Hence, secθ = (2√61)/12 = √61/6