Android – how to align the imagebutton to the right in the horizontal LinearLayout

I have an imagebutton in the LinearLayout. I try to put the imagebutton to the right of the horizontal LinearLayout. I use layout_ Gravity = "right" but it doesn't work. Please help me

 <LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:weightSum="5"
    tools:context="com.startsoft.musicalsound.MainActivity" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="0.3"
        android:background="@drawable/img_bg_header"
        android:orientation="horizontal" >

        <ImageButton
            android:id="@+id/btn_menu"
            android:layout_width="30dp"
            android:layout_height="30dp"
            android:layout_gravity="right"
            android:background="@android:color/transparent"
            android:src="@drawable/ic_action_sort_by_size" />
    </LinearLayout>

resolvent:

Use Android: gravity = "right" on the parent layout of imagebutton. You can also delete Android: layout from it_ gravity =“right”.