Question

the mean of marks obtained by 15 student is 63 if marks of two student were written wrongly 73 instead of 78 and 59 instead of 64 find the new mean​

Answer 1

Answer:

455

Step-by-step explanation:

1.  In quadrilateral ACBD, AC = AD and AB bisects ∠A )see figure). Show that ΔABC ≌ ΔABD. What can you say about BC and BD?



Ans. In quadrilateral ABCD we have

                  AC = AD

            and AB being the bisector of ∠A.

            Now, in ΔABC and ΔABD,

                  AC = AD

[Given]

                  AB = AB

[Common]

∠CAB = ∠DAB [∴ AB bisects ∠CAD]

            ∴ Using SAS criteria, we have

                  ΔABC ≌ ΔABD.

            ∴ Corresponding parts of congruent triangles (c.p.c.t) are equal.

            ∴ BC = BD.

2.  ABCD is a quadrilateral in which AD = BC and ∠DAB = ∠CBA (see Figure). Prove that

      (i) ΔABD ≌ ΔBAC

      (ii) BD = AC

      (iii) ∠ABD = ∠BAC.