diff --git a/놀이터(예제 코드 작성)/solid-design-pattern-sample/README.md b/놀이터(예제 코드 작성)/solid-design-pattern-sample/README.md
index b2bea4b..bb6276a 100644
--- a/놀이터(예제 코드 작성)/solid-design-pattern-sample/README.md	
+++ b/놀이터(예제 코드 작성)/solid-design-pattern-sample/README.md	
@@ -64,6 +64,12 @@
 
 ### 전략(Strategy) 패턴
 
+#### 구현 요구사항
+
+- 연령대별로 물건의 할인된 금액 계산기를 구현한다.
+    - 아이일 경우 할인율은 15%이다.
+    - 어른일 경우 할인율은 30%이다.
+
 ### 템플릿 메서드(Template Method) 패턴
 
 ### 상태(State) 패턴
diff --git a/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/AgeTypeAfter.kt b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/AgeTypeAfter.kt
new file mode 100644
index 0000000..dd707c7
--- /dev/null
+++ b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/AgeTypeAfter.kt	
@@ -0,0 +1,6 @@
+package com.banjjoknim.soliddesignpatternsample.designpattern.strategy.after
+
+enum class AgeTypeAfter(val discountPolicy: DiscountPolicy) {
+    KIDS(DiscountPolicy { price -> price * 70 / 100 }),
+    ADULTS(DiscountPolicy { price -> price * 90 / 100 }),
+}
diff --git a/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/PriceCalculatorAfter.kt b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/PriceCalculatorAfter.kt
new file mode 100644
index 0000000..665156c
--- /dev/null
+++ b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/PriceCalculatorAfter.kt	
@@ -0,0 +1,11 @@
+package com.banjjoknim.soliddesignpatternsample.designpattern.strategy.after
+
+class PriceCalculatorAfter {
+    fun calculate(price: Int, discountPolicy: DiscountPolicy): Int {
+        return discountPolicy.calculate(price)
+    }
+}
+
+fun interface DiscountPolicy {
+    fun calculate(price: Int): Int
+}
diff --git a/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/PriceCalculatorApplicationAfter.kt b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/PriceCalculatorApplicationAfter.kt
new file mode 100644
index 0000000..5de0bc1
--- /dev/null
+++ b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/after/PriceCalculatorApplicationAfter.kt	
@@ -0,0 +1,11 @@
+package com.banjjoknim.soliddesignpatternsample.designpattern.strategy.after
+
+class PriceCalculatorApplicationAfter
+
+fun main() {
+    val priceCalculator = PriceCalculatorAfter()
+    val price = 10000
+    val ageType = AgeTypeAfter.KIDS
+    val calculatedPrice = priceCalculator.calculate(price, ageType.discountPolicy)
+    println(calculatedPrice)
+}
diff --git a/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/AgeTypeBefore.kt b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/AgeTypeBefore.kt
new file mode 100644
index 0000000..8e52a9d
--- /dev/null
+++ b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/AgeTypeBefore.kt	
@@ -0,0 +1,6 @@
+package com.banjjoknim.soliddesignpatternsample.designpattern.strategy.before
+
+enum class AgeTypeBefore {
+    KIDS,
+    ADULTS,
+}
diff --git a/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/PriceCalculatorApplicationBefore.kt b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/PriceCalculatorApplicationBefore.kt
new file mode 100644
index 0000000..d3dcc1f
--- /dev/null
+++ b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/PriceCalculatorApplicationBefore.kt	
@@ -0,0 +1,11 @@
+package com.banjjoknim.soliddesignpatternsample.designpattern.strategy.before
+
+class PriceCalculatorApplicationBefore
+
+fun main() {
+    val priceCalculator = PriceCalculatorBefore()
+    val price = 10000
+    val ageTypeBefore = AgeTypeBefore.ADULTS
+    val calculatedPrice = priceCalculator.calculate(price, ageTypeBefore)
+    println(calculatedPrice)
+}
diff --git a/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/PriceCalculatorBefore.kt b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/PriceCalculatorBefore.kt
new file mode 100644
index 0000000..b0764b8
--- /dev/null
+++ b/놀이터(예제 코드 작성)/solid-design-pattern-sample/src/main/kotlin/com/banjjoknim/soliddesignpatternsample/designpattern/strategy/before/PriceCalculatorBefore.kt	
@@ -0,0 +1,10 @@
+package com.banjjoknim.soliddesignpatternsample.designpattern.strategy.before
+
+class PriceCalculatorBefore {
+    fun calculate(price: Int, ageType: AgeTypeBefore): Int {
+        return when (ageType) {
+            AgeTypeBefore.KIDS -> price * 70 / 100
+            AgeTypeBefore.ADULTS -> price * 85 / 100
+        }
+    }
+}