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Math Problems
Grade 6
Simple interest
A group consisting of
21
21
21
aggressive zombies triples in size every hour. Which equation matches the number of zombies after
4
4
4
hours?
\newline
Z
=
21
(
3
)
4
Z=21(3)^{4}
Z
=
21
(
3
)
4
\newline
Z
=
3
(
21
)
4
Z=3(21)^{4}
Z
=
3
(
21
)
4
\newline
Z
=
3
(
21
)
(
21
)
(
21
)
(
21
)
Z=3(21)(21)(21)(21)
Z
=
3
(
21
)
(
21
)
(
21
)
(
21
)
\newline
Z
=
21
(
3
)
(
3
)
Z=21(3)(3)
Z
=
21
(
3
)
(
3
)
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A group consisting of
23
23
23
aggressive zombies triples in size every hour. Which equation matches the number of zombies after
2
2
2
hours?
\newline
Z
=
23
(
3
)
2
Z=23(3)^{2}
Z
=
23
(
3
)
2
\newline
Z
=
3
(
1
+
23
)
2
Z=3(1+23)^{2}
Z
=
3
(
1
+
23
)
2
\newline
Z
=
23
(
1
+
3
)
2
Z=23(1+3)^{2}
Z
=
23
(
1
+
3
)
2
\newline
Z
=
3
(
23
)
(
23
)
Z=3(23)(23)
Z
=
3
(
23
)
(
23
)
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The formula for simple interest is
I
=
P
r
t
I=P r t
I
=
P
r
t
, where
I
I
I
is the interest earned,
P
P
P
is the principal,
r
r
r
is the interest rate and
t
t
t
is the number of years. Solve the formula for
r
r
r
in terms of
P
,
I
P, I
P
,
I
and
t
t
t
.
\newline
Answer:
r
=
r=
r
=
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