diff --git a/kmath-for-real/src/commonMain/kotlin/scientifik/kmath/real/DoubleMatrixOperations.kt b/kmath-for-real/src/commonMain/kotlin/scientifik/kmath/real/DoubleMatrixOperations.kt
index d9c6b5eab..7eeba3031 100644
--- a/kmath-for-real/src/commonMain/kotlin/scientifik/kmath/real/DoubleMatrixOperations.kt
+++ b/kmath-for-real/src/commonMain/kotlin/scientifik/kmath/real/DoubleMatrixOperations.kt
@@ -57,7 +57,7 @@ operator fun Double.times(matrix: Matrix<Double>) = MatrixContext.real.produce(m
 }
 
 operator fun Double.plus(matrix: Matrix<Double>) = MatrixContext.real.produce(matrix.rowNum, matrix.colNum) {
-    row, col -> this * matrix[row, col]
+    row, col -> this + matrix[row, col]
 }
 
 operator fun Double.minus(matrix: Matrix<Double>) = MatrixContext.real.produce(matrix.rowNum, matrix.colNum) {
diff --git a/kmath-for-real/src/commonTest/kotlin/scientific.kmath.real/RealMatrixTest.kt b/kmath-for-real/src/commonTest/kotlin/scientific.kmath.real/RealMatrixTest.kt
index 808794442..31b8b5252 100644
--- a/kmath-for-real/src/commonTest/kotlin/scientific.kmath.real/RealMatrixTest.kt
+++ b/kmath-for-real/src/commonTest/kotlin/scientific.kmath.real/RealMatrixTest.kt
@@ -1,8 +1,9 @@
 package scientific.kmath.real
 
-import scientifik.kmath.real.average
-import scientifik.kmath.real.realMatrix
-import scientifik.kmath.real.sum
+import scientifik.kmath.real.*
+import scientifik.kmath.linear.VirtualMatrix
+import scientifik.kmath.linear.build
+import scientifik.kmath.structures.Matrix
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
@@ -13,4 +14,144 @@ class RealMatrixTest {
         assertEquals(m.sum(), 900.0)
         assertEquals(m.average(), 9.0)
     }
+
+    @Test
+    fun testSequenceToMatrix() {
+        val m = Sequence<DoubleArray> {
+            listOf(
+                    DoubleArray(10) { 10.0 },
+                    DoubleArray(10) { 20.0 },
+                    DoubleArray(10) { 30.0 }).iterator()
+        }.toMatrix()
+        assertEquals(m.sum(), 20.0 * 30)
+    }
+
+    @Test
+    fun testRepeatStackVertical() {
+        val matrix1 = Matrix.build<Double>(2, 3)(
+                1.0, 0.0, 0.0,
+                0.0, 1.0, 2.0
+        )
+        val matrix2 = Matrix.build<Double>(6, 3)(
+                1.0, 0.0, 0.0,
+                0.0, 1.0, 2.0,
+                1.0, 0.0, 0.0,
+                0.0, 1.0, 2.0,
+                1.0, 0.0, 0.0,
+                0.0, 1.0, 2.0
+        )
+        assertEquals(VirtualMatrix.wrap(matrix2), matrix1.repeatStackVertical(3))
+    }
+
+    @Test
+    fun testMatrixAndDouble() {
+        val matrix1 = Matrix.build<Double>(2, 3)(
+                1.0, 0.0, 3.0,
+                4.0, 6.0, 2.0
+        )
+        val matrix2 = (matrix1 * 2.5 + 1.0 - 2.0) / 2.0
+        val expectedResult = Matrix.build<Double>(2, 3)(
+                0.75, -0.5, 3.25,
+                4.5, 7.0, 2.0
+        )
+        assertEquals(matrix2, expectedResult)
+    }
+
+    @Test
+    fun testDoubleAndMatrix() {
+        val matrix1 = Matrix.build<Double>(2, 3)(
+                1.0, 0.0, 3.0,
+                4.0, 6.0, 2.0
+        )
+        val matrix2 = 20.0 - (10.0 + (5.0 * matrix1))
+        //val matrix2 = 10.0 + (5.0 * matrix1)
+        val expectedResult = Matrix.build<Double>(2, 3)(
+                5.0, 10.0, -5.0,
+                -10.0, -20.0, 0.0
+        )
+        assertEquals(matrix2, expectedResult)
+    }
+
+    @Test
+    fun testSquareAndPower() {
+        val matrix1 = Matrix.build<Double>(2, 3)(
+                -1.0, 0.0, 3.0,
+                4.0, -6.0, -2.0
+        )
+        val matrix2 = Matrix.build<Double>(2, 3)(
+                1.0, 0.0, 9.0,
+                16.0, 36.0, 4.0
+        )
+        val matrix3 = Matrix.build<Double>(2, 3)(
+                -1.0, 0.0, 27.0,
+                64.0, -216.0, -8.0
+        )
+        assertEquals(matrix1.square(), matrix2)
+        assertEquals(matrix1.pow(3), matrix3)
+    }
+
+    @Test
+    fun testTwoMatrixOperations() {
+        val matrix1 = Matrix.build<Double>(2, 3)(
+                -1.0, 0.0, 3.0,
+                4.0, -6.0, 7.0
+        )
+        val matrix2 = Matrix.build<Double>(2, 3)(
+                1.0, 0.0, 3.0,
+                4.0, 6.0, -2.0
+        )
+        val result = matrix1 * matrix2 + matrix1 - matrix2
+        val expectedResult = Matrix.build<Double>(2, 3)(
+                -3.0, 0.0, 9.0,
+                16.0, -48.0, -5.0
+        )
+        assertEquals(result, expectedResult)
+    }
+
+    @Test
+    fun testColumnOperations() {
+        val matrix1 = Matrix.build<Double>(2, 4)(
+                -1.0, 0.0, 3.0, 15.0,
+                4.0, -6.0, 7.0, -11.0
+        )
+        val matrix2 = Matrix.build<Double>(2, 5)(
+                -1.0, 0.0, 3.0, 15.0, -1.0,
+                4.0, -6.0, 7.0, -11.0, 4.0
+        )
+        val col1 = Matrix.build<Double>(2, 1)(0.0, -6.0)
+        val cols1to2 = Matrix.build<Double>(2, 2)(
+                0.0, 3.0,
+                -6.0, 7.0
+        )
+        assertEquals(matrix1.appendColumn { it[0] }, matrix2)
+        assertEquals(matrix1.extractColumn(1), col1)
+        assertEquals(matrix1.extractColumns(1..2), cols1to2)
+        assertEquals(matrix1.sumByColumn(), Matrix.build<Double>(4, 1)(3.0, -6.0, 10.0, 4.0))
+        assertEquals(matrix1.minByColumn(), Matrix.build<Double>(4, 1)(-1.0, -6.0, 3.0, -11.0))
+        assertEquals(matrix1.maxByColumn(), Matrix.build<Double>(4, 1)(4.0, 0.0, 7.0, 15.0))
+        assertEquals(matrix1.averageByColumn(), Matrix.build<Double>(4, 1)(1.5, -3.0, 5.0, 2.0))
+    }
+
+    @Test
+    fun testAllElementOperations() {
+        val matrix1 = Matrix.build<Double>(2, 4)(
+                -1.0, 0.0, 3.0, 15.0,
+                4.0, -6.0, 7.0, -11.0
+        )
+        assertEquals(matrix1.sum(), 11.0)
+        assertEquals(matrix1.min(), -11.0)
+        assertEquals(matrix1.max(), 15.0)
+        assertEquals(matrix1.average(), 1.375)
+    }
+
+//    fun printMatrix(m: Matrix<Double>) {
+//        for (row in 0 until m.shape[0]) {
+//            for (col in 0 until m.shape[1]) {
+//                print(m[row, col])
+//                print(" ")
+//            }
+//            println()
+//        }
+//    }
+
 }