Add, subtract and scale vectors

Grade 10 Math Worksheet - Challenge Me

Circle the best answer.

1. 1.

   A student claims |u − v| = |u| − |v|. With u = ⟨12, 5⟩ and v = ⟨3, 4⟩ that gives 13 − 5 = 8. Kira checks it. What does Kira find?

   • The claim fails: u − v = ⟨9, 1⟩ has length √82, about 9.1, not 8
   • The claim holds: 13 − 5 = 8, and both lengths are exact whole numbers
   • The claim fails: u − v = ⟨15, 9⟩ has length about 17.5
   • The claim fails: u − v = ⟨9, 1⟩ has length 82, not 8
2. 2.

   One knot is one nautical mile per hour. Luz tracks two ferries leaving one dock: A at ⟨12, 5⟩ knots and B at ⟨-4, -7⟩ knots. How far apart are they after 2 hours?

   • 20 nautical miles
   • 1,600 nautical miles
   • 40 nautical miles
   • About 42.1 nautical miles
3. 3.

   A sled track passes through P(1, 2) and Q(7, 5). Ari places flag R(13, k) on the same straight line. Which k works?

   • k = 11
   • k = 10
   • k = 8
   • k = 6
4. 4.

   Tala's quilt has corners A(0, 0), B(6, 2), C(10, 7) and D(3, 5) in order. Tala asks if ABCD is a parallelogram. Which reasoning is correct?

   • Yes: AB and DC both rise 2 units, so those two sides must be parallel
   • No: AB = ⟨6, 2⟩ but DC = ⟨7, 2⟩, so opposite sides are not equal vectors
   • No: the diagonals AC and BD have different lengths, and a parallelogram's must match
   • Yes: AB + BC = AD + DC = ⟨10, 7⟩, so the sides add the same
5. 5.

   Pia's two rocket paths ⟨3, k⟩ and ⟨-12, 20⟩ lie along one line. Which k works, and do the paths point the same way?

   • k = -5; they point the same way, because a multiplier below 1 just shrinks
   • k = 5; they point the same way, because 20 ÷ 4 = 5
   • k = -5; they point opposite ways, because the multiplier is -1/4
   • k = -80; they point opposite ways, because -12 ÷ 3 = -4
6. 6.

   Zee's quilt is parallelogram ABCD with A at the origin, AB = u = ⟨6, 0⟩ and AD = v = ⟨2, 4⟩. M is the midpoint of side DC. Which vector is AM?

   • ⟨7, 2⟩, which is u + ½v
   • ⟨-1, 4⟩, which is v − ½u
   • ⟨4, 2⟩, which is ½(u + v)
   • ⟨5, 4⟩, which is v + ½u
7. 7.

   Two vectors satisfy u + v = ⟨5, 1⟩ and u − v = ⟨1, 7⟩. Jun's car and trailer move with u + v = ⟨5, 1⟩ and u − v = ⟨1, 7⟩. Which pair gives u and v?

   • u = ⟨3, 4⟩ and v = ⟨-2, 3⟩
   • u = ⟨2, -3⟩ and v = ⟨3, 4⟩
   • u = ⟨6, 8⟩ and v = ⟨4, -6⟩
   • u = ⟨3, 4⟩ and v = ⟨2, -3⟩
8. 8.

   Milo's drone log shows positions from the start of (4, 3), (8, 6) and (12, 10) km after 1, 2 and 3 hours. Milo claims constant velocity. What does the log show?

   • Not constant: the hourly slides are ⟨4, 3⟩, ⟨4, 3⟩ and ⟨4, 4⟩, so hour 3 differs
   • Constant: the first two hours match, so the third reading must be a small error
   • Constant: the run grows by exactly 4 km in each hour
   • Not constant: the distances from the start are 5, 10 and about 15.6 km, so they grow
9. 9.

   Bo's robot slides u = ⟨3, 4⟩, then turns a quarter turn left and slides the same distance. Where does it finish, as one slide from the start?

   • ⟨7, 1⟩
   • ⟨6, 8⟩
   • ⟨7, 7⟩
   • ⟨-1, 7⟩

10. Read this first

    Use this

    |u| = 5, |v| = 10. u + v = ⟨-2, 11⟩, so |u + v|² = 4 + 121 = 125.

11. 10.

    Luz tests u = ⟨4, 3⟩ and v = ⟨-6, 8⟩. Their lengths are 5 and 10, and |u + v| = √125. What does 5² + 10² = 125 show?

    • u and v point the same way, so the lengths add and |u + v| = 15
    • u and v are perpendicular, so u + v closes a right triangle with legs 5 and 10
    • Nothing: 125 is a coincidence that depends on these particular numbers
    • u and v point opposite ways, so |u + v| = 10 − 5 = 5, the lengths' difference