Question

Students have organized

Answer 1

Answer:

Part A. At least 6 hours

Part B.  In less than 2.5 hours Elijah will be behind Mercedes

Part C.  In more than 2.5 hours Elijah will be ahead Aubrey

Step-by-step explanation:

D = distance

v =speed

t = time

Formula connecting D, v and t:

$D=v\cdot t$

Part A.

Steve's speed: $v=3.5\ mph$

Distance: at least 21 miles

Time: unknown, so

$3.5\cdot t\ge 21\\ \\35t\ge 210\ [\text{Multiplied by 10}]\\ \\t\ge \dfrac{210}{35}\\ \\t\ge \dfrac{30}{5}\\ \\t\ge 6$

It would take Steve at least 6 hours to walk at least 21 mi on Day 1.

Part B.

Mercedes's speed: $v_M=2.4\ mph$

Elijan's speed: $v_E=3.2\ mph$

Elijan's Distance walked: $D_E$ miles

Mercedes's Distance walked: $D_M$ miles

Time: x hours

Mercedes is 2 miles ahead, so

$D_E=3.2x\\ \\D_M=2.4x+2$

Elijan will be behind when

$D_E$

In 2.5 hours Elijan will catch up Mercedes, and in less than 2.5 hours Elijah will be behind Mercedes.

Part C.

Aubrey's speed: $v_M=3\ mph$

Elijan's speed: $v_E=3.2\ mph$

Elijan's Distance walked: $D_E$ miles

Aubrey's Distance walked: $D_A$ miles

Time: x hours

At the beginning of Day 3, Elijah starts walking at the marker for Mile 42,  and Aubrey starts walking at the marker for Mile 42.5.

$D_E=42+3.2x\\ \\D_A=42.5+3x$

Elijan will be ahead of Aubrey when

$D_E>D_A\\ \\42+3.2x> 42.5+3x\\ \\3.2x-3x>42.5-42\\ \\0.2x>0.5\\ \\2x>5\ [\text{Multiplied by 10}]\\ \\x>\dfrac{5}{2}\\ \\x>2.5\ hours$

In 2.5 hours Elijan will catch up Aubrey, and in more than 2.5 hours Elijah will be ahead Aubrey.