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3 years ago

HELP HELP HELP Sally can paint a room in 4 hours. Joe can paint a room in 6 hours. How

Mathematics

2 answers:

Dmitry [639]3 years ago

6 0

Answer:

2 hrs, 24 min

Step-by-step explanation:

Sally: in one hour, she can paint 1/4 of the room.

Joe: in one our, he can paint 1/6 of the room

Hour one: 1/4+1/6=3/12+2/12=5/12

1÷5/12=1*12/5=12/5

12/5= 2 & 2/5 hours, or 2.4 hours, or 2 hrs 24 minutes

Vesnalui [34]3 years ago

3 0

Answer: 2.4 hours

Step-by-step explanation:

1/4 1/6

LCM

3/12+2/12=5/12 repricical 12/5 =2.4

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the tens digit of a two digit is 7. if the order of the digit is reversed the new number obtained is 45 less than the original n

kirill [66]

9514 1404 393

Answer:

Step-by-step explanation:

The difference of 45 means the difference of digits in the number is 45/9 = 5. So, the ones digit is 7-5 = 2, and the number is 72.

If you want an equation, you can use x for the ones digit.

70 +x = 45 +(10x +7)

18 = 9x . . . . . . . . . . . . . subtract 52+x from both sides

2 = x

The ones digit is 2, so the number is 72.

_____

Further explanation

If you start with the two digits xy in a number and reverse them, the difference between the numbers xy and yx is ...

(10x +y) -(10y +x) = 9(x -y)

This tells you the difference between the digit-reversed numbers is 9 times the difference between the digits.

5 0

3 years ago

Read 2 more answers

The number of ducks and pigs in a field totals 38. The total number of legs among them is 94 assuming each duck has exactly two

Reika [66]

Answer:

22 pigs and 3 ducks

Step-by-step explanation:

22 pigs would make 88 legs and 3 ducks will make 6 legs so u add that together and you get 94 legs (smile) ik i'm smart lol

8 0

4 years ago

Please help and thank you

hram777 [196]

Answer:

First one

Step-by-step explanation:

The formula is y-y=m(x-x)

Since the coordinates are negatives. Double negatives make positive.

Hope that helps:)

7 0

3 years ago

Hi, could someone help me differentiate Q6 b with the use if ln

Lady bird [3.3K]

Answer:

$\displaystyle \frac{dy}{dx} = \frac{-(2x - 3)(6x - 43)}{(3x + 4)^4}$

General Formulas and Concepts:

Pre-Algebra

Equality Properties

Algebra II

Natural logarithms ln and Euler's number e
Logarithmic Property [Dividing]: $\displaystyle log(\frac{a}{b}) = log(a) - log(b)$
Logarithmic Property [Exponential]: $\displaystyle log(a^b) = b \cdot log(a)$

Calculus

Differentiation

Derivatives
Derivative Notation
Implicit Differentiation

Derivative Property [Multiplied Constant]: $\displaystyle \frac{d}{dx} [cf(x)] = c \cdot f'(x)$

Derivative Property [Addition/Subtraction]: $\displaystyle \frac{d}{dx}[f(x) + g(x)] = \frac{d}{dx}[f(x)] + \frac{d}{dx}[g(x)]$

Basic Power Rule:

f(x) = cxⁿ
f’(x) = c·nxⁿ⁻¹

Derivative Rule [Quotient Rule]: $\displaystyle \frac{d}{dx} [\frac{f(x)}{g(x)} ]=\frac{g(x)f'(x)-g'(x)f(x)}{g^2(x)}$

Derivative Rule [Chain Rule]: $\displaystyle \frac{d}{dx}[f(g(x))] =f'(g(x)) \cdot g'(x)$

Step-by-step explanation:

Step 1: Define

Identify

$\displaystyle y = \frac{(2x - 3)^2}{(3x + 4)^3}$

Step 2: Rewrite

[Equality Property] ln both sides: $\displaystyle lny = ln \bigg[ \frac{(2x - 3)^2}{(3x + 4)^3} \bigg]$
Expand [Logarithmic Property - Dividing]: $\displaystyle lny = ln(2x - 3)^2 - ln(3x + 4)^3$
Simplify [Logarithmic Property - Exponential]: $\displaystyle lny = 2ln(2x - 3) - 3ln(3x + 4)$

Step 3: Differentiate

Implicit Differentiation: $\displaystyle \frac{dy}{dx}[lny] = \frac{dy}{dx} \bigg[ 2ln(2x - 3) - 3ln(3x + 4) \bigg]$
Logarithmic Differentiation [Derivative Rule - Chain Rule]: $\displaystyle \frac{1}{y} \ \frac{dy}{dx} = 2 \bigg( \frac{1}{2x - 3} \bigg)\frac{dy}{dx}[2x - 3] - 3 \bigg( \frac{1}{3x + 4} \bigg) \frac{dy}{dx}[3x + 4]$
Basic Power Rule: $\displaystyle \frac{1}{y} \ \frac{dy}{dx} = 4 \bigg( \frac{1}{2x - 3} \bigg) - 9 \bigg( \frac{1}{3x + 4} \bigg)$
Simplify: $\displaystyle \frac{1}{y} \ \frac{dy}{dx} = \frac{4}{2x - 3} - \frac{9}{3x + 4}$
Isolate $\displaystyle \frac{dy}{dx}$ : $\displaystyle \frac{dy}{dx} = y \bigg( \frac{4}{2x - 3} - \frac{9}{3x + 4} \bigg)$
Substitute in y [Derivative]: $\displaystyle \frac{dy}{dx} = \frac{(2x - 3)^2}{(3x + 4)^3} \bigg( \frac{4}{2x - 3} - \frac{9}{3x + 4} \bigg)$
Simplify: $\displaystyle \frac{dy}{dx} = \frac{(2x - 3)^2}{(3x + 4)^3} \bigg[ \frac{4(3x + 4) - 9(2x - 3)}{(2x - 3)(3x +4)} \bigg]$
Simplify: $\displaystyle \frac{dy}{dx} = \frac{-(2x - 3)(6x - 43)}{(3x + 4)^4}$