Someone plz help me!
1 answer:
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Answer:
15 years old
Step-by-step explanation:
Start by defining the variables that we are going to use throughout our working:
Let the current age of Wei Ling and Wei Xuan be L and X years old respectively.
Next, form equations using the given information.
<u>5 years </u><u>ago</u>
Wei Ling: (L -5) years old
Wei Xuan: (X -5) years old
Given that the ratio of Wei Ling's age to that of Wei Xuan's is 2: 5,
Cross multiply:
2(X -5)= 5(L -5)
Expand:
2X -10= 5L -25
2X= 5L -25 +10
2X= 5L -15 -----(1)
<u>9 years time</u>
Wei Ling: (L +9) years old
Wei Xuan: (X +9) years old
Given that the ratio of Wei Ling's age to that of Wei Xuan is 3: 4,
Cross multiply:
3(X +9)= 4(L +9)
Expand:
3X +27= 4L +36
3X= 4L +36 -27
3X= 4L +9 -----(2)
Let's solve using the elimination method.
(1) ×3:
6X= 15L -45 -----(3)
(2) ×2:
6X= 8L +18 -----(4)
(3) -(4):
6X -6X= 15L -45 -(8L +18)
0= 15L -45 -8L -18
0= 7L -63
7L= 63
L= 63 ÷7
L= 9
Substitute L= 9 into (1):
2X= 5(9) -15
2X= 45 -15
2X= 30
X= 30 ÷2
X= 15
Thus, Wei Xuan is 15 years old now.
Answer:
Option (B).
Step-by-step explanation:
Percentage change between two numbers a and b can be calculated by the formula,
% change =
Where, (b - a) = Change in values
a = Initial value
If a = 16 and b = 20
Percentage change between 16 and 20 will be,
=
=
= 25%
If a = 20 and b = 16,
Percentage change =
= 20%
Therefore, %change between 16 and 24 may be 16% or 20%.
Option (A),
= 25%
Option (B),
= 1.25 - 1 × 100
= 1.25 - 100
= -98.75%
Option (C),
= 25%
Option (D),
= 20%
Therefore, we can not use the calculation used in Option (B).